feat(briefing): hard-cut tear-down

Backend:
- Delete briefing services (pipeline, scheduler, conversations, profile, tools)
- Delete routes/briefing.py + remove blueprint registration
- Move _get_temp_unit into services/weather.get_temp_unit (reads top-level temp_unit setting)
- Rename briefing_preferences.py → rss_filtering.py (functions are RSS-specific)
- Strip briefing scheduler hooks from app.py
- Strip briefing scheduler call from routes/settings.py
- Update test imports (test_rss_service, test_tz_helpers)

Frontend:
- Delete BriefingView, BriefingSetupWizard, BriefingToolStatusRow
- Strip /briefing route + nav links (AppHeader, KnowledgeView)
- Strip Settings → Briefing tab + state + functions + imports
- Strip briefing-intermediate handling from ChatMessage
- Hide /news route + nav links (NewsView depended on briefing endpoints; orphaned in tree)
- Drop unused useSettingsStore from AppHeader

The Android BriefingScreen lives in a separate repo and is not touched here.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_rss_service.py

@@ -84,7 +84,7 @@ async def test_classify_items_batch_handles_llm_failure():
 
 def test_score_rss_items_excludes_blacklisted_topics():
     """Items with excluded topics should be removed."""
-    from fabledassistant.services.briefing_preferences import score_and_filter_items
+    from fabledassistant.services.rss_filtering import score_and_filter_items
 
     items = [
         {"id": 1, "title": "Tech news", "topics": ["technology"], "published_at": "2026-03-25T08:00:00"},
@@ -104,7 +104,7 @@ def test_score_rss_items_excludes_blacklisted_topics():
 
 def test_score_rss_items_boosts_included_topics():
     """Items matching include_topics should rank higher than neutral items."""
-    from fabledassistant.services.briefing_preferences import score_and_filter_items
+    from fabledassistant.services.rss_filtering import score_and_filter_items
 
     items = [
         {"id": 1, "title": "Random news", "topics": ["other"], "published_at": "2026-03-25T07:00:00"},
@@ -122,7 +122,7 @@ def test_score_rss_items_boosts_included_topics():
 
 def test_score_rss_items_no_preferences_returns_all():
     """With no preferences, all items should be returned sorted by recency."""
-    from fabledassistant.services.briefing_preferences import score_and_filter_items
+    from fabledassistant.services.rss_filtering import score_and_filter_items
 
     items = [
         {"id": 1, "title": "A", "topics": [], "published_at": "2026-03-24T10:00:00"},