Refactor Docker setup and add mock data support

- Updated .dockerignore and .gitignore for better file management.
- Introduced .env.example for environment variable configuration.
- Added docker-compose.dev.yml for development with mock data and live reload.
- Enhanced Dockerfile to include necessary dependencies and entrypoint script.
- Created mock_data.py to provide sample data for testing without OpenStack/Prometheus.
- Added unit tests for template filters in dashboard.
- Cleaned up various files for consistency and improved readability.

docker-compose.dev.yml

@@ -0,0 +1,22 @@
+# Development override: use with
+#   docker compose -f docker-compose.yml -f docker-compose.dev.yml up --build
+#
+# Uses mock data (no OpenStack/Prometheus), mounts code for live reload.
+
+services:
+  watcher-visio:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    volumes:
+      - .:/app
+    environment:
+      - USE_MOCK_DATA=true
+      - DEBUG=true
+      - PYTHONUNBUFFERED=1
+    ports:
+      - "8000:8000"
+    # Optional: skip entrypoint migrations on every start for faster restart
+    # command: ["python3", "manage.py", "runserver", "0.0.0.0:8000"]
+    stdin_open: true
+    tty: true