refactor: extract star/notification/badge helpers into database.py and add enrich_items content module

Introduce `update_target_stars`, `get_target_owner_uid`, and `VOTABLE_TARGETS`/`STAR_TARGETS` in database.py; replace inline badge insertion with `award_badge()` and inline notification creation with `create_notification()` across auth, comments, and follow routers; add `enrich_items()` in new content module to centralize post/gist list assembly and remove duplicated enrichment logic from feed and gists routers.

devplacepy/routers/follow.py

@@ -3,8 +3,7 @@ from datetime import datetime, timezone
 from fastapi import APIRouter, Request
 from fastapi.responses import RedirectResponse
 from devplacepy.database import get_table
-from devplacepy.templating import clear_unread_cache
-from devplacepy.utils import generate_uid, require_user
+from devplacepy.utils import generate_uid, require_user, create_notification
 
 logger = logging.getLogger(__name__)
 router = APIRouter()
@@ -30,17 +29,7 @@ async def follow_user(request: Request, username: str):
         "created_at": datetime.now(timezone.utc).isoformat(),
     })
 
-    notifications = get_table("notifications")
-    notifications.insert({
-        "uid": generate_uid(),
-        "user_uid": target["uid"],
-        "type": "follow",
-        "message": f"{user['username']} started following you",
-        "related_uid": user["uid"],
-        "read": False,
-        "created_at": datetime.now(timezone.utc).isoformat(),
-    })
-    clear_unread_cache(target["uid"])
+    create_notification(target["uid"], "follow", f"{user['username']} started following you", user["uid"])
 
     logger.info(f"{user['username']} followed {username}")
     return RedirectResponse(url=f"/profile/{username}", status_code=302)