feat: migrate SQLAlchemy from 1.4 to 2.0 with ORM style

- Remove encode/databases dependency, use native SQLAlchemy 2.0 async
- Convert all table definitions to Declarative Mapping pattern
- Update all controllers to accept session parameter (dependency injection)
- Convert all queries from Core style to ORM style
- Remove PostgreSQL compatibility checks (PostgreSQL only now)
- Add proper typing for engine and session factories

server/migrations/env.py

@@ -3,7 +3,7 @@ from logging.config import fileConfig
 from alembic import context
 from sqlalchemy import engine_from_config, pool
 
-from reflector.db import metadata
+from reflector.db.base import metadata
 from reflector.settings import settings
 
 # this is the Alembic Config object, which provides
@@ -25,8 +25,7 @@ target_metadata = metadata
 # ... etc.
 
 
-# don't use asyncpg for the moment
-settings.DATABASE_URL = settings.DATABASE_URL.replace("+asyncpg", "")
+# No need to modify URL, using sync engine from db module
 
 
 def run_migrations_offline() -> None: