Add public feed, admin area, self-registration, visibility & hashtags

- Public feed (/) with infinite scroll via Intersection Observer
- Self-registration (/register)
- Admin area (/admin/entries, /admin/users) with user management
- journal_entries: visibility (public/private) + hashtags fields
- users: is_admin flag
- DB schema updated (recreate DB to apply)
- CI: run go test via docker run (golang:1.25-alpine) — fixes 'go not found'

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -24,7 +24,12 @@ jobs:
         run: printf 'DB_PASSWORD=%s\n' '${{ secrets.DB_PASSWORD }}' > ${{ vars.DEPLOY_DIR }}/.env
 
       - name: Test
-        run: cd ${{ vars.DEPLOY_DIR }}/backend && go test ./...
+        run: |
+          docker run --rm \
+            -v ${{ vars.DEPLOY_DIR }}/backend:/app \
+            -w /app \
+            golang:1.25-alpine \
+            go test ./...
 
       - name: Build & Deploy
         run: docker compose -f ${{ vars.DEPLOY_DIR }}/docker-compose.yml up --build -d