Add alembic DB schema management (#86)

* Use alembic
* add creation helper
* example migration tool

create_example_migration.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""
+Script to create a blank migration for manual editing.
+
+Usage:
+    ./env/bin/python create_example_migration.py
+
+This creates an empty migration file that you can manually edit to add
+custom migration logic (data migrations, complex schema changes, etc.)
+
+Unlike create_migration.py which auto-generates from model changes,
+this creates a blank template for you to fill in.
+"""
+
+import os
+import sys
+
+# Add current directory to path
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+
+from alembic.config import Config
+
+from alembic import command
+
+# Create Alembic config
+alembic_cfg = Config("alembic.ini")
+
+# Set database URL from meshview config
+try:
+    from meshview.config import CONFIG
+
+    database_url = CONFIG["database"]["connection_string"]
+    alembic_cfg.set_main_option("sqlalchemy.url", database_url)
+    print(f"Using database URL from config: {database_url}")
+except Exception as e:
+    print(f"Warning: Could not load meshview config: {e}")
+    print("Using default database URL")
+    alembic_cfg.set_main_option("sqlalchemy.url", "sqlite+aiosqlite:///packets.db")
+
+# Generate blank migration
+try:
+    print("Creating blank migration for manual editing...")
+    command.revision(alembic_cfg, autogenerate=False, message="Manual migration")
+    print("✓ Successfully created blank migration!")
+    print("\nNow edit the generated file in alembic/versions/")
+    print("Add your custom upgrade() and downgrade() logic")
+except Exception as e:
+    print(f"✗ Error creating migration: {e}")
+    import traceback
+
+    traceback.print_exc()
+    sys.exit(1)