fix(backend): auto-generate tag seed data from hashtags in items.json

[mahula]

Motivation

While implementing E2E tests for the TipTap rich text editor integration (PR #670), we discovered that clicking hashtags in item popups did not trigger map filtering.

Investigation revealed that the seed data (items.json) contains items with hashtags (e.g., #sustainability, #community), but the tags collection was empty. The hashtag click handler only triggers filtering when it finds a matching tag registered in the backend.

Current Status (on main)

1. Start and seed the application
2. Open http://localhost:8080 and click on "Community Garden Berlin" marker
3. Click any hashtag (e.g., #sustainability) in the popup
4. Result: Nothing happens - the tags collection is empty, so filtering silently fails
5. Verify: curl http://localhost:8055/items/tags returns {"data":[]}

Solution

Extended backend/prepare-seed.js to automatically:

• Extract all #hashtag patterns from text fields in items.json
• Generate tags.json with unique tags and auto-assigned colors
• Preserve existing tag colors when re-running the script

The generated tags.json is added to .gitignore since it's derived from items.json.

How to Test

1. Checkout this branch and start fresh: docker compose down && sudo rm -rf ./data/database && docker compose up -d
2. Wait for Directus, then seed: cd backend && ./push.sh && ./seed.sh
3. Observe output: "Found 34 unique hashtag(s)" and "Written 34 tag(s) to tags.json"
4. Open http://localhost:8080 and click on "Community Garden Berlin" marker
5. Click #sustainability in the popup
6. Expected: URL updates to ?tags=sustainability and map filters accordingly
7. Verify: curl http://localhost:8055/items/tags returns 34 tags