fix: move Alembic to package submodule for Docker compatibility

- Move alembic/ directory to nextcloud_mcp_server/alembic/ subpackage
- Update migrations.py to use package location instead of alembic.ini
- Update env.py to set script_location dynamically
- Update alembic.ini for development CLI usage
- Fix Dockerfile typo: .vnev -> .venv

This fixes FileNotFoundError when running in Docker with non-editable
install. The alembic package is now installed with the main package,
making it work in both development and production environments.

Resolves: Docker startup error 'alembic.ini not found at
/app/.venv/lib/python3.12/site-packages/alembic.ini'

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

alembic.ini

@@ -2,7 +2,7 @@
 
 [alembic]
 # Path to migration scripts
-script_location = alembic
+script_location = nextcloud_mcp_server/alembic
 
 # Template used to generate migration file names
 # Default: %%(rev)s_%%(slug)s
@@ -26,7 +26,7 @@ timezone = utc
 
 # Version location specification
 # Supports single or multiple directories
-version_locations = alembic/versions
+version_locations = nextcloud_mcp_server/alembic/versions
 
 # Path separator for version locations (required to suppress deprecation warning)
 # Use os (for cross-platform compatibility)