persist public url in settings

[shubham3121]

This pull request introduces a persistent settings system for managing the application's public URL, moving the source of truth from in-memory config to a database-backed singleton table. It adds a new settings table, a corresponding SQLModel entity, a repository for CRUD operations, and updates the handler and initialization logic to use this new persistence layer. The public URL is now consistently managed through the database, with initialization from environment variables if set.

Database & Persistence Layer:

• Added a new Alembic migration to create a settings table with fields for id, public_url, and updated_at (e18675e6eecb_add_settings_table.py).
• Introduced the Settings SQLModel entity and a SettingsRepository for CRUD operations on the singleton settings row. [1] [2]

Settings Handling Logic:

• Refactored SettingsHandler to use SettingsRepository for all reads/writes of the public URL, making the database the source of truth. Added an initialize_from_config method to sync environment/config values to the database on startup. [1] [2] [3] [4]

Application Initialization:

• Updated main.py to instantiate and register the new SettingsRepository and SettingsHandler, and to call initialize_from_config at startup. The app now updates the database (not just config) when the public URL is set via ngrok or environment variable. [1] [2] [3] [4]

Imports & Module Exports:

• Updated imports and __all__ exports to include the new Settings entity and SettingsRepository in the settings component.

These changes ensure that the application's public URL is reliably persisted and synchronized across restarts and deployments, supporting future extensibility for other settings.