refactor: simplify architecture and harden lifecycle

Remove obsolete implementations, centralize background task ownership and terminal-state recovery, consolidate frontend routing and log streaming, and enforce project-wide verification in CI.

server/internal/service/test_database_test.go

@@ -0,0 +1,22 @@
+package service
+
+import (
+	"testing"
+
+	"gorm.io/gorm"
+)
+
+// closeTestDatabase releases SQLite file handles before testing.TempDir cleanup.
+// Windows does not permit removal of an open database file.
+func closeTestDatabase(t *testing.T, db *gorm.DB) {
+	t.Helper()
+	sqlDB, err := db.DB()
+	if err != nil {
+		t.Fatalf("get test database handle: %v", err)
+	}
+	t.Cleanup(func() {
+		if err := sqlDB.Close(); err != nil {
+			t.Errorf("close test database: %v", err)
+		}
+	})
+}