feat: add AI email extraction with Cloudflare Workers AI

Add AI-powered email content extraction feature using Cloudflare Workers AI to automatically identify and extract important information from emails including verification codes, authentication links, service links, and subscription links.

Features:
- AI extraction with priority-based logic (auth_code > auth_link > service_link > subscription_link > other_link)
- Admin allowlist configuration with wildcard support (*@example.com)
- Frontend display in both email list (compact) and detail view (full mode)
- Bilingual documentation (Chinese/English)
- Database migration: add metadata field to raw_mails (v0.0.3 -> v0.0.4)

Technical highlights:
- Proper regex escaping for wildcard pattern matching
- Content truncation to avoid AI token limits
- Error handling that won't affect email receiving
- JSON schema validation for AI responses
- Type-safe TypeScript implementation
- Vue I18n support with special character escaping

References:
- Inspired by Alle Project: https://github.com/bestruirui/Alle
- Uses Cloudflare Workers AI JSON Mode

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

worker/src/admin_api/db_api.ts

@@ -9,6 +9,7 @@ CREATE TABLE IF NOT EXISTS raw_mails (
     source TEXT,
     address TEXT,
     raw TEXT,
+    metadata TEXT,
     created_at DATETIME DEFAULT CURRENT_TIMESTAMP
 );
 
@@ -142,8 +143,11 @@ export default {
             const query = `ALTER TABLE address ADD password TEXT;`
             await c.env.DB.exec(query);
         }
+        if (version == "v0.0.3") {
+            // migration from v0.0.3 to v0.0.4
+            await c.env.DB.exec(`ALTER TABLE raw_mails ADD COLUMN metadata TEXT;`);
+        }
         if (version != CONSTANTS.DB_VERSION) {
-            // TODO: Perform migration logic here
             // remove all \r and \n characters from the query string
             // split by ; and join with a ;\n
             const query = DB_INIT_QUERIES.replace(/[\r\n]/g, "")