🐛 fix(app): 为稳定期首次连接增加瞬时网络重试保护 (#309)

## 问题背景
在 app 启动后等待 20s 以上，再手动触发数据库连接时，遇到瞬时网络错误（如 `no route to
host`）会立即失败，用户体感为“没有重试”。

相关讨论与上下文参考：
- https://github.com/Syngnat/GoNavi/pull/294

## 问题描述
此前重试保护逻辑主要以“应用启动窗口（20s）”为边界：
- 启动窗口内：瞬时网络失败会自动重试
- 启动窗口外：即使是瞬时网络失败也不重试
这导致“用户首次手动连接发生在稳定期”时，行为与预期不一致。

## 本地复现关键日志（节选）
```log
2026/03/27 15:21:04.792462 [INFO] 应用启动完成（首次连接保护窗口=20s，最多重试=4 次）
2026/03/27 15:22:29.196794 [INFO] 获取数据库连接：... 启动阶段=稳定期(age=1m24.405s)
2026/03/27 15:22:29.208920 [ERROR] 建立数据库连接失败：... connect: no route to host
2026/03/27 15:22:29.212453 [ERROR] DBGetDatabases 获取连接失败：... connect: no route to host


2026/03/27 16:07:45.463959 [INFO] 获取数据库连接：... 启动阶段=稳定期(age=21s)
2026/03/27 16:07:45.470744 [ERROR] 建立数据库连接失败：... connect: no route to host
2026/03/27 16:07:45.473604 [WARN] 检测到瞬时网络失败，准备重试连接：... 尝试=1/4 延迟=800ms
2026/03/27 16:07:46.277658 [INFO] 获取数据库连接：... 启动阶段=稳定期(age=21.814s)
2026/03/27 16:07:46.281761 [INFO] 创建数据库驱动实例：... 尝试=2/4
2026/03/27 16:07:46.284741 [ERROR] 建立数据库连接失败：... connect: no route to host
2026/03/27 16:20:59.298636 [INFO] 应用启动完成（首次连接保护窗口=20s，最多重试=4 次）
2026/03/27 16:23:26.180978 [INFO] 获取数据库连接：... 启动阶段=稳定期(age=2m26.883s)
2026/03/27 16:23:26.201478 [INFO] 数据库连接成功并写入缓存：...
```

## 变更内容
- 调整连接重试判定逻辑：
  - 启动窗口内：保持原有重试预算（最多 4 次）
  - 启动窗口外：若为瞬时网络错误，补充一次保护重试（总计 2 次尝试）
  - 非瞬时错误（如认证失败）在稳定期不重试
- 日志文案泛化，避免“仅启动期”误导：
  - 数据库连接在重试后成功
  - 检测到瞬时网络失败，准备重试连接
## 测试与验证
### 新增/更新单元测试覆盖以下场景：
- 启动期瞬时错误重试并成功
- 稳定期瞬时错误重试一次并成功
- 稳定期瞬时错误持续失败时，仅重试一次后停止
- 稳定期非瞬时错误不重试
- 稳定期重试路径输出重试提示日志
- 启动期瞬时错误失败时使用完整重试预算
### 本地执行：
- go test ./internal/app -run StartupRetry -count=1
- go test ./internal/app -count=1
### 影响范围
- 连接建立重试策略（internal/app/app.go）
- 启动重试相关测试（internal/app/app_startup_connect_retry_test.go）
## 风险与回滚
- 风险：稳定期瞬时网络错误会增加一次重试等待（约 800ms）
- 回滚：可回退本 PR 即恢复“仅启动窗口重试”的旧策略

internal/app/app.go

@@ -608,7 +608,7 @@ func (a *App) connectDatabaseWithStartupRetry(rawConfig connection.ConnectionCon
 
 		if err := dbInst.Connect(connectConfig); err == nil {
 			if attempt > 1 {
-				logger.Warnf("数据库连接在启动保护重试后成功：%s 缓存Key=%s 尝试=%d/%d", formatConnSummary(effectiveConfig), cacheKey, attempt, startupConnectRetryAttempts)
+				logger.Warnf("数据库连接在重试后成功：%s 缓存Key=%s 尝试=%d/%d", formatConnSummary(effectiveConfig), cacheKey, attempt, startupConnectRetryAttempts)
 			}
 			return dbInst, effectiveConfig, nil
 		} else {
@@ -616,10 +616,10 @@ func (a *App) connectDatabaseWithStartupRetry(rawConfig connection.ConnectionCon
 			wrapped := wrapConnectError(effectiveConfig, err)
 			lastErr = wrapped
 			logger.Error(wrapped, "建立数据库连接失败：%s 缓存Key=%s", formatConnSummary(effectiveConfig), cacheKey)
-			if !a.shouldRetryStartupConnect(err, attempt) {
+			if !a.shouldRetryConnect(err, attempt) {
 				return nil, effectiveConfig, wrapped
 			}
-			logger.Warnf("检测到启动期瞬时网络失败，准备重试连接：%s 缓存Key=%s 尝试=%d/%d 延迟=%s 原因=%s",
+			logger.Warnf("检测到瞬时网络失败，准备重试连接：%s 缓存Key=%s 尝试=%d/%d 延迟=%s 原因=%s",
 				formatConnSummary(effectiveConfig), cacheKey, attempt, startupConnectRetryAttempts, startupConnectRetryDelay, normalizeErrorMessage(err))
 			time.Sleep(startupConnectRetryDelay)
 		}
@@ -650,18 +650,21 @@ func (a *App) startupPhaseLabel() string {
 	return fmt.Sprintf("稳定期(age=%s)", age)
 }
 
-func (a *App) shouldRetryStartupConnect(err error, attempt int) bool {
+func (a *App) shouldRetryConnect(err error, attempt int) bool {
 	if attempt >= startupConnectRetryAttempts {
 		return false
 	}
-	if a == nil || a.startedAt.IsZero() {
+	if !isTransientStartupConnectError(err) {
 		return false
 	}
-	age := time.Since(a.startedAt)
-	if age < 0 || age > startupConnectRetryWindow {
-		return false
+	if a != nil && !a.startedAt.IsZero() {
+		age := time.Since(a.startedAt)
+		if age >= 0 && age <= startupConnectRetryWindow {
+			return true
+		}
 	}
-	return isTransientStartupConnectError(err)
+	// Outside startup window, still grant one retry for transient network glitches.
+	return attempt == 1
 }
 
 func isTransientStartupConnectError(err error) bool {

internal/app/app_startup_connect_retry_test.go

@@ -2,11 +2,14 @@ package app
 
 import (
 	"errors"
+	"os"
+	"strings"
 	"testing"
 	"time"
 
 	"GoNavi-Wails/internal/connection"
 	"GoNavi-Wails/internal/db"
+	"GoNavi-Wails/internal/logger"
 )
 
 type fakeStartupRetryDB struct {
@@ -106,7 +109,7 @@ func TestConnectDatabaseWithStartupRetry_RetriesTransientFailureAndReappliesGlob
 	}
 }
 
-func TestConnectDatabaseWithStartupRetry_DoesNotRetryOutsideStartupWindow(t *testing.T) {
+func TestConnectDatabaseWithStartupRetry_RetriesOnceOutsideStartupWindow(t *testing.T) {
 	originalNewDatabaseFunc := newDatabaseFunc
 	originalResolveDialConfigWithProxyFunc := resolveDialConfigWithProxyFunc
 	defer func() {
@@ -130,12 +133,165 @@ func TestConnectDatabaseWithStartupRetry_DoesNotRetryOutsideStartupWindow(t *tes
 	a := &App{startedAt: time.Now().Add(-startupConnectRetryWindow - time.Second)}
 	rawConfig := connection.ConnectionConfig{Type: "postgres", Host: "10.1.131.86", Port: 5432, User: "postgres"}
 
+	_, _, err := a.connectDatabaseWithStartupRetry(rawConfig)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if connectCalls != 2 {
+		t.Fatalf("expected 2 connect attempts outside startup window, got %d", connectCalls)
+	}
+}
+
+func TestConnectDatabaseWithStartupRetry_DoesNotRetryOutsideStartupWindowForNonTransientError(t *testing.T) {
+	originalNewDatabaseFunc := newDatabaseFunc
+	originalResolveDialConfigWithProxyFunc := resolveDialConfigWithProxyFunc
+	defer func() {
+		newDatabaseFunc = originalNewDatabaseFunc
+		resolveDialConfigWithProxyFunc = originalResolveDialConfigWithProxyFunc
+	}()
+
+	connectCalls := 0
+	newDatabaseFunc = func(dbType string) (db.Database, error) {
+		return &fakeStartupRetryDB{
+			connect: func(config connection.ConnectionConfig) error {
+				connectCalls++
+				return errors.New("pq: password authentication failed")
+			},
+		}, nil
+	}
+	resolveDialConfigWithProxyFunc = func(raw connection.ConnectionConfig) (connection.ConnectionConfig, error) {
+		return raw, nil
+	}
+
+	a := &App{startedAt: time.Now().Add(-startupConnectRetryWindow - time.Second)}
+	rawConfig := connection.ConnectionConfig{Type: "postgres", Host: "10.1.131.86", Port: 5432, User: "postgres"}
+
 	_, _, err := a.connectDatabaseWithStartupRetry(rawConfig)
 	if err == nil {
 		t.Fatal("expected error, got nil")
 	}
 	if connectCalls != 1 {
-		t.Fatalf("expected 1 connect attempt outside startup window, got %d", connectCalls)
+		t.Fatalf("expected 1 connect attempt outside startup window for non-transient error, got %d", connectCalls)
+	}
+}
+
+func TestConnectDatabaseWithStartupRetry_LogsRetryHintOutsideStartupWindow(t *testing.T) {
+	originalNewDatabaseFunc := newDatabaseFunc
+	originalResolveDialConfigWithProxyFunc := resolveDialConfigWithProxyFunc
+	defer func() {
+		newDatabaseFunc = originalNewDatabaseFunc
+		resolveDialConfigWithProxyFunc = originalResolveDialConfigWithProxyFunc
+	}()
+
+	logPath := logger.Path()
+	beforeSize := int64(0)
+	if fi, err := os.Stat(logPath); err == nil {
+		beforeSize = fi.Size()
+	}
+
+	connectCalls := 0
+	newDatabaseFunc = func(dbType string) (db.Database, error) {
+		return &fakeStartupRetryDB{
+			connect: func(config connection.ConnectionConfig) error {
+				connectCalls++
+				if connectCalls == 1 {
+					return errors.New("dial tcp 10.1.131.86:5432: connect: no route to host")
+				}
+				return nil
+			},
+		}, nil
+	}
+	resolveDialConfigWithProxyFunc = func(raw connection.ConnectionConfig) (connection.ConnectionConfig, error) {
+		return raw, nil
+	}
+
+	a := &App{startedAt: time.Now().Add(-startupConnectRetryWindow - time.Second)}
+	rawConfig := connection.ConnectionConfig{Type: "postgres", Host: "10.1.131.86", Port: 5432, User: "postgres"}
+
+	_, _, err := a.connectDatabaseWithStartupRetry(rawConfig)
+	if err != nil {
+		t.Fatalf("expected success after retry, got error: %v", err)
+	}
+	if connectCalls != 2 {
+		t.Fatalf("expected 2 connect attempts, got %d", connectCalls)
+	}
+
+	logContent, readErr := os.ReadFile(logPath)
+	if readErr != nil {
+		t.Fatalf("read log failed: %v", readErr)
+	}
+	if int64(len(logContent)) < beforeSize {
+		t.Fatalf("expected log file to grow, before=%d after=%d", beforeSize, len(logContent))
+	}
+	appended := string(logContent[beforeSize:])
+	if !strings.Contains(appended, "检测到瞬时网络失败，准备重试连接") {
+		t.Fatalf("expected retry hint log in appended segment, got: %s", appended)
+	}
+}
+
+func TestConnectDatabaseWithStartupRetry_OutsideStartupWindowTransientFailureStopsAfterOneRetry(t *testing.T) {
+	originalNewDatabaseFunc := newDatabaseFunc
+	originalResolveDialConfigWithProxyFunc := resolveDialConfigWithProxyFunc
+	defer func() {
+		newDatabaseFunc = originalNewDatabaseFunc
+		resolveDialConfigWithProxyFunc = originalResolveDialConfigWithProxyFunc
+	}()
+
+	connectCalls := 0
+	newDatabaseFunc = func(dbType string) (db.Database, error) {
+		return &fakeStartupRetryDB{
+			connect: func(config connection.ConnectionConfig) error {
+				connectCalls++
+				return errors.New("dial tcp 10.1.131.86:5432: connect: no route to host")
+			},
+		}, nil
+	}
+	resolveDialConfigWithProxyFunc = func(raw connection.ConnectionConfig) (connection.ConnectionConfig, error) {
+		return raw, nil
+	}
+
+	a := &App{startedAt: time.Now().Add(-startupConnectRetryWindow - time.Second)}
+	rawConfig := connection.ConnectionConfig{Type: "postgres", Host: "10.1.131.86", Port: 5432, User: "postgres"}
+
+	_, _, err := a.connectDatabaseWithStartupRetry(rawConfig)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if connectCalls != 2 {
+		t.Fatalf("expected 2 connect attempts outside startup window for transient error, got %d", connectCalls)
+	}
+}
+
+func TestConnectDatabaseWithStartupRetry_StartupWindowTransientFailureUsesFullRetryBudget(t *testing.T) {
+	originalNewDatabaseFunc := newDatabaseFunc
+	originalResolveDialConfigWithProxyFunc := resolveDialConfigWithProxyFunc
+	defer func() {
+		newDatabaseFunc = originalNewDatabaseFunc
+		resolveDialConfigWithProxyFunc = originalResolveDialConfigWithProxyFunc
+	}()
+
+	connectCalls := 0
+	newDatabaseFunc = func(dbType string) (db.Database, error) {
+		return &fakeStartupRetryDB{
+			connect: func(config connection.ConnectionConfig) error {
+				connectCalls++
+				return errors.New("dial tcp 10.1.131.86:5432: connect: no route to host")
+			},
+		}, nil
+	}
+	resolveDialConfigWithProxyFunc = func(raw connection.ConnectionConfig) (connection.ConnectionConfig, error) {
+		return raw, nil
+	}
+
+	a := &App{startedAt: time.Now()}
+	rawConfig := connection.ConnectionConfig{Type: "postgres", Host: "10.1.131.86", Port: 5432, User: "postgres"}
+
+	_, _, err := a.connectDatabaseWithStartupRetry(rawConfig)
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if connectCalls != startupConnectRetryAttempts {
+		t.Fatalf("expected %d connect attempts in startup window, got %d", startupConnectRetryAttempts, connectCalls)
 	}
 }