Move ai-stack and paintplus vendored source under vendor/

Matches the existing vendor/easy-asterisk convention (used by
services/asterisk.sh) instead of two one-off top-level directories that
cluttered the repo root and didn't look like anything else next to
setup.sh, lib/, services/, extras/. Only the two services' own SRC_DIR
path resolution and header comments needed updating — nothing else in
the repo referenced the old ./ai-stack / ./paintplus paths.

Also documents vendor/ in README.md's Layout section.

vendor/paintplus/scripts/init_database.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+"""
+Initialize the database before other startup scripts run.
+
+This ensures the database exists and has all required tables
+before download_sample_eyes.py tries to use it.
+"""
+
+import os
+import sys
+from pathlib import Path
+
+# Add backend to path - handle both Docker and local environments
+# In Docker: backend is at /app/
+# Locally: backend is at ./backend/
+if Path('/app').exists():
+    sys.path.insert(0, '/app')
+else:
+    sys.path.insert(0, str(Path(__file__).parent.parent / 'backend'))
+
+def main():
+    # Import after path setup
+    from app.database import engine, Base, init_db
+    from app.models import project, user, patch
+
+    print("Initializing database...")
+
+    # Create all tables
+    init_db()
+
+    # Verify database was created - check both Docker and local paths
+    docker_db_path = Path('/app/data/ai_photo_edit.db')
+    local_db_path = Path('./data/ai_photo_edit.db')
+
+    if docker_db_path.exists():
+        print(f"✓ Database initialized at: {docker_db_path}")
+    elif local_db_path.exists():
+        print(f"✓ Database initialized at: {local_db_path}")
+    else:
+        print("⚠ Database file not found at expected locations, but tables may still be created")
+
+    print("Database initialization complete.")
+
+if __name__ == '__main__':
+    main()