feat: structured user profile with LLM-learned preferences

Replaces the freeform briefing-profile note with a DB-backed user_profiles
table. Users can edit job/industry/expertise/response preferences/interests/
work schedule via a new Settings → Profile tab. The LLM appends nightly
observations; at 14+ entries they are auto-consolidated into a learned_summary.
Profile context is injected into both briefing and chat system prompts.

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

src/fabledassistant/services/briefing_scheduler.py

@@ -208,7 +208,7 @@ async def _run_profile_closeout(user_id: int, model: str) -> None:
     Read yesterday's briefing conversation, extract preference observations,
     and append them to the briefing profile note.
     """
-    from fabledassistant.services.briefing_profile import append_observations
+    from fabledassistant.services.user_profile import append_observations
     from fabledassistant.services.briefing_pipeline import _llm_synthesise
     from fabledassistant.models.conversation import Conversation, Message