feat: add pre-commit hooks for local CI checks

- Black (auto-fix formatting on commit)
- Flake8 (block on syntax errors and undefined names)
- Bandit (security scan, non-blocking to match CI)
- Tests (run on pre-push only)
- Apply Black formatting fixes caught by the new hooks

utils/diagnostics.py

@@ -137,10 +137,12 @@ class GalleryDiagnostics:
                 self.logger.info(f"   [NOTE] Prompts in database: {prompt_count}")
 
                 # Check if generated_images table exists
-                cursor = conn.execute("""
+                cursor = conn.execute(
+                    """
                     SELECT name FROM sqlite_master 
                     WHERE type='table' AND name='generated_images'
-                """)
+                """
+                )
 
                 has_images_table = cursor.fetchone() is not None
                 self.logger.info(f"   [IMG]  Images table exists: {has_images_table}")
@@ -174,10 +176,12 @@ class GalleryDiagnostics:
                 conn.row_factory = sqlite3.Row
 
                 # Check if table exists
-                cursor = conn.execute("""
+                cursor = conn.execute(
+                    """
                     SELECT name FROM sqlite_master 
                     WHERE type='table' AND name='generated_images'
-                """)
+                """
+                )
 
                 if not cursor.fetchone():
                     return {
@@ -191,13 +195,15 @@ class GalleryDiagnostics:
                 self.logger.info(f"   [STATS] Images in database: {image_count}")
 
                 # Get recent images
-                cursor = conn.execute("""
+                cursor = conn.execute(
+                    """
                     SELECT gi.*, p.text 
                     FROM generated_images gi 
                     LEFT JOIN prompts p ON gi.prompt_id = p.id 
                     ORDER BY gi.generation_time DESC 
                     LIMIT 5
-                """)
+                """
+                )
                 recent_images = [dict(row) for row in cursor.fetchall()]
 
                 self.logger.info(f"   [TIME] Recent images: {len(recent_images)}")