Add node tag import functionality to collector

- Add tag_import.py module with JSON file parsing and database upsert
- Convert collector CLI to group with subcommands for extensibility
- Add 'import-tags' command to import tags from JSON file
- Update docker-compose.yml.example with separated data directories:
  - data/collector for tags.json
  - data/web for members.json
- Add import-tags Docker service for easy containerized imports
- Add example data files in example/data/collector and example/data/web
- Add comprehensive test coverage (20 tests) for tag import

example/data/web/members.json

@@ -0,0 +1,10 @@
+{
+  "members": [
+    {
+      "name": "Example Member",
+      "callsign": "N0CALL",
+      "role": "Network Operator",
+      "description": "Example member entry"
+    }
+  ]
+}