Complete LinkSyncServer and LinkSyncExtension implementation

LinkSyncServer:
- Fix app.py imports, add CORS middleware, lifespan events
- Create api/routes.py router aggregator
- Create config/settings.py for centralized configuration
- Rewrite models/base.py with proper relationships and serialization
- Rewrite all API endpoints with real DB integration (auth, links, collections, sync, queries, tags)
- Add admin endpoints (user management, stats, audit log)
- Complete query parser with recursive descent and proper precedence
- Complete query executor with set operations and field filters
- Set up Alembic migrations with initial schema
- Create web interface (templates, CSS, JS)
- Add 42 passing tests (auth, links, collections, queries)
- Add deploy.ps1 and deploy.sh scripts
- Update README with deployment workflow

LinkSyncExtension:
- Create utils/api.js (REST client with retries, auth, error handling)
- Create utils/sync.js (3 sync modes + conflict detection)
- Create utils/collection.js (collection management)
- Create utils/query-engine.js (client-side query parser)
- Rewrite background.js (sync loop, bookmark events, message routing)
- Rewrite popup.js (tabs, settings modal, notifications, CRUD)
- Update popup.html (tabbed interface, query builder, modal)
- Update popup.css (full redesign)
- Create content/content.js (page metadata extraction)
- Create options.html/js (dedicated settings page)
- Generate icons (48x48, 96x96)
- Update manifest.json (host permissions, content scripts, options)
- Create AGENTS.md

LinkSyncServer/config/settings.py

@@ -0,0 +1,31 @@
+"""
+LinkSyncServer - Application Settings
+"""
+
+import os
+from pathlib import Path
+
+BASE_DIR = Path(__file__).resolve().parent.parent
+
+
+class Settings:
+    DATABASE_URL: str = os.environ.get(
+        "DATABASE_URL", "sqlite:///linksync.db"
+    )
+    SECRET_KEY: str = os.environ.get("SECRET_KEY", "dev-secret-key-change-in-production")
+    ADMIN_USERNAME: str = os.environ.get("ADMIN_USERNAME", "admin")
+    ADMIN_PASSWORD: str = os.environ.get("ADMIN_PASSWORD", "admin123")
+    DEBUG: bool = os.environ.get("DEBUG", "False").lower() in ("true", "1", "yes")
+    HOST: str = os.environ.get("HOST", "0.0.0.0")
+    PORT: int = int(os.environ.get("PORT", "5000"))
+    CORS_ORIGINS: str = os.environ.get("CORS_ORIGINS", "http://localhost:5555")
+    JWT_ALGORITHM: str = "HS256"
+    JWT_ACCESS_TOKEN_EXPIRE_MINUTES: int = 1440
+    BCRYPT_COST_FACTOR: int = 12
+    RATE_LIMIT_REQUESTS: int = 100
+    RATE_LIMIT_WINDOW: int = 60
+    LOGIN_RATE_LIMIT: int = 10
+    LOGIN_RATE_LIMIT_WINDOW: int = 3600
+
+
+settings = Settings()