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/utils/database.py

@@ -2,8 +2,10 @@
 """Database utilities for database operations.
 
 This module provides utility functions and classes to interact with a database using SQLAlchemy. It includes:
-- Creating a database engine with connection pooling.
+- Creating a PostgreSQL database engine with connection pooling.
 - Generating a session factory for creating sessions.
+
+Note: This project uses PostgreSQL only. SQLite is not supported.
 """
 
 import logging
@@ -16,31 +18,35 @@ logger = logging.getLogger(__name__)
 
 
 def get_db_engine(database_url: str):
-    """Create a database engine with connection pooling.
+    """Create a PostgreSQL database engine with connection pooling.
 
     Args:
-        database_url (str): The URL string to connect to the database. It can be for SQLite or PostgreSQL databases.
+        database_url (str): The PostgreSQL URL string to connect to the database.
 
     Returns:
-        sqlalchemy.engine.Engine: A SQLAlchemy Engine instance configured according to the provided database URL.
+        sqlalchemy.engine.Engine: A SQLAlchemy Engine instance configured for PostgreSQL.
+
+    Raises:
+        ValueError: If database_url is not a PostgreSQL URL.
     """
-    if database_url.startswith("sqlite"):
-        # Configuration for SQLite database
-        engine = create_engine(
-            database_url, connect_args={"check_same_thread": False}, echo=False
-        )
-    else:
-        # Configuration for PostgreSQL databases with connection pooling
-        engine = create_engine(
-            database_url,
-            poolclass=QueuePool,
-            pool_size=10,
-            max_overflow=20,
-            pool_pre_ping=True,
-            echo=False,
+    if not database_url.startswith("postgresql"):
+        raise ValueError(
+            f"Unsupported database: {database_url.split(':')[0]}. "
+            "Only PostgreSQL is supported."
         )
 
-    logger.info(f"Database engine created for: {database_url.split('@')[0]}@...")
+    engine = create_engine(
+        database_url,
+        poolclass=QueuePool,
+        pool_size=10,
+        max_overflow=20,
+        pool_pre_ping=True,
+        echo=False,
+    )
+
+    # Log URL without password
+    safe_url = database_url.split("@")[0] + "@..." if "@" in database_url else database_url
+    logger.info(f"Database engine created for: {safe_url}")
     return engine