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/wrangler.toml.template

@@ -107,6 +107,10 @@ ENABLE_AUTO_REPLY = false
 # REMOVE_EXCEED_SIZE_ATTACHMENT = true
 # remove all attachment, mail maybe mising some information due to parsing
 # REMOVE_ALL_ATTACHMENT = true
+# AI email extraction, automatically extract verification codes, auth links, etc.
+# ENABLE_AI_EMAIL_EXTRACT = true
+# AI model name, choose from https://developers.cloudflare.com/workers-ai/models/#text-generation
+# AI_EXTRACT_MODEL = "@cf/meta/llama-3.1-8b-instruct"
 # Calling other woker to process email
 # ENABLE_ANOTHER_WORKER = false
 # ANOTHER_WORKER_LIST = """
@@ -127,6 +131,10 @@ binding = "DB"
 database_name = "xxx"
 database_id = "xxx"
 
+# Workers AI binding (required for AI email extraction)
+# [ai]
+# binding = "AI"
+
 # kv config for send email verification code
 # [[kv_namespaces]]
 # binding = "KV"