chore: PostgreSQL migration compatibility and infrastructure improvements

Database & Migrations:
- Update all Alembic migrations for PostgreSQL compatibility
- Remove SQLite-specific syntax (AUTOINCREMENT, etc.)
- Add database utility helpers for PostgreSQL operations
- Fix services to use PostgreSQL-compatible queries

Documentation:
- Add comprehensive Docker deployment guide
- Add production deployment documentation
- Add infrastructure architecture documentation
- Update database setup guide for PostgreSQL-only
- Expand troubleshooting guide

Architecture & Validation:
- Add migration.yaml rules for SQL compatibility checking
- Enhance validate_architecture.py with migration validation
- Update architecture rules to validate Alembic migrations

Development:
- Fix duplicate install-all target in Makefile
- Add Celery/Redis validation to install.py script
- Add docker-compose.test.yml for CI testing
- Add squash_migrations.py utility script
- Update tests for PostgreSQL compatibility
- Improve test fixtures in conftest.py

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/core/database.py

@@ -3,45 +3,33 @@
 Database configuration and session management.
 
 This module provides classes and functions for:
-- Database engine creation and configuration
+- PostgreSQL database engine creation and configuration
 - Session management with connection pooling
 - Database dependency for FastAPI routes
+
+Note: This project uses PostgreSQL only. SQLite is not supported.
 """
 
 import logging
 
-from sqlalchemy import create_engine, event
+from sqlalchemy import create_engine
 from sqlalchemy.orm import declarative_base, sessionmaker
+from sqlalchemy.pool import QueuePool
 
-from .config import settings
+from .config import settings, validate_database_url
 
+# Validate database URL on import
+validate_database_url()
 
-def _configure_sqlite_connection(dbapi_connection, connection_record):
-    """Configure SQLite connection for better concurrency.
-
-    - WAL mode: Allows concurrent reads during writes
-    - busy_timeout: Wait up to 30 seconds if database is locked
-    - synchronous=NORMAL: Balance between safety and performance
-    """
-    cursor = dbapi_connection.cursor()
-    cursor.execute("PRAGMA journal_mode=WAL")
-    cursor.execute("PRAGMA busy_timeout=30000")
-    cursor.execute("PRAGMA synchronous=NORMAL")
-    cursor.close()
-
-
-# Create engine with SQLite-specific configuration
-engine_kwargs = {}
-
-# Add SQLite-specific settings for better concurrent access
-if settings.database_url.startswith("sqlite"):
-    engine_kwargs["connect_args"] = {"check_same_thread": False}
-
-engine = create_engine(settings.database_url, **engine_kwargs)
-
-# Configure SQLite pragmas on connection
-if settings.database_url.startswith("sqlite"):
-    event.listen(engine, "connect", _configure_sqlite_connection)
+# Create PostgreSQL engine with connection pooling
+engine = create_engine(
+    settings.database_url,
+    poolclass=QueuePool,
+    pool_size=10,
+    max_overflow=20,
+    pool_pre_ping=True,
+    echo=False,
+)
 
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)