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>

frontend/src/router/index.ts

@@ -116,16 +116,6 @@ const router = createRouter({
       name: "calendar",
       component: () => import("@/views/CalendarView.vue"),
     },
-    {
-      path: "/briefing",
-      name: "briefing",
-      component: () => import("@/views/BriefingView.vue"),
-    },
-    {
-      path: "/news",
-      name: "news",
-      component: () => import("@/views/NewsView.vue"),
-    },
     {
       path: "/settings",
       name: "settings",