feat: add leaderboard router, gamification backfill, and shared content creation helpers

Introduce a new `/leaderboard` endpoint ranking top 50 members by total stars, wire it into the app router and documentation. Implement `_backfill_gamification()` in `database.py` to compute XP/levels for existing accounts from prior posts, comments, votes, and follows. Extract `is_owner()`, `create_content_item()`, and `detail_context()` into `content.py` to centralize content creation, reward awarding, mention notifications, and attachment linking. Update comment creation/deletion in `comments.py` to use `award_rewards()` with `XP_COMMENT` and the new `is_owner()` helper. Add shared template partials documentation for vote bars, star buttons, post headers, and topic selectors to `AGENTS.md`.

devplacepy/services/news.py

@@ -15,6 +15,7 @@ NEWS_API_URL_DEFAULT = "https://news.app.molodetz.nl/api"
 AI_URL_DEFAULT = "https://openai.app.molodetz.nl/v1/chat/completions"
 AI_MODEL_DEFAULT = "molodetz"
 GRADE_THRESHOLD_DEFAULT = 7
+GRADE_MAX_TOKENS = 2000
 
 
 def _get_ai_key() -> str:
@@ -216,7 +217,7 @@ class NewsService(BaseService):
         payload = {
             "model": ai_model,
             "messages": [{"role": "user", "content": prompt}],
-            "max_tokens": 10,
+            "max_tokens": GRADE_MAX_TOKENS,
             "temperature": 0.0,
         }