v2.0.0: Production Architecture — PostgreSQL, Celery & Strict Typing

This release graduates TermSub from a single-file prototype to a production-ready, horizontally-scalable architecture.

🏗️ Architecture Overhaul

PostgreSQL replaces SQLite

• Full concurrent access support for multi-worker deployments
• Proper connection pooling and transaction safety
• Production-grade backup and replication ready

Celery + Redis Distributed Task Queue

• Background jobs are now handled by Celery workers instead of a single-threaded local queue
• Redis Pub/Sub for real-time WebSocket broadcasts from distributed workers
• Heartbeat monitoring, timeout recovery, and retry logic at the Celery level

Modern SQLAlchemy 2.0

• Migrated to Mapped[] / mapped_column() type-safe ORM declarations
• Proper session lifecycle management with get_db_session() context managers

🔧 Code Quality

Strict Static Typing

• Full MyPy strict = true compliance across the codebase
• Replaced legacy Optional[X] and List[X] with modern X | None and list[X] syntax
• Explicit return type annotations on all functions

Linting & Formatting Pipeline

• Added Ruff for fast linting, import sorting, and code formatting
• Added MyPy for static type checking
• GitHub Actions CI runs both on every push to main

🗄️ Database & Migrations

• New migration: add_celery_task_id_column.py for Celery task tracking
• Enhanced schema validation on startup with clear error messages for outdated databases

📊 Stats

37 files changed, +3,142 / −2,584 lines