Add SQLAlchemy ORM with Alembic migrations

- Added SQLAlchemy 2.0 and Alembic 1.13 dependencies
- Created models.py with Channel and VideoEntry ORM models
- Created database.py for database configuration and session management
- Initialized Alembic migration system with initial migration
- Updated feed_parser.py with save_to_db() method for persistence
- Updated main.py with database initialization and new API routes:
  - /api/feed now saves to database by default
  - /api/channels lists all tracked channels
  - /api/history/<channel_id> returns video history
- Updated .gitignore to exclude database files
- Updated CLAUDE.md with comprehensive ORM and migration documentation

Database uses SQLite (yottob.db) with upsert logic to avoid duplicates.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

pyproject.toml

@@ -5,6 +5,8 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.14"
 dependencies = [
+    "alembic>=1.13.0",
     "feedparser>=6.0.12",
     "flask>=3.1.2",
+    "sqlalchemy>=2.0.0",
 ]