Phase 3: coaching preferences + weekly check-in engine

Add coaching preferences (auto-derived from the profile, user-overridable) and
a periodic check-in engine that quotes the person's own words and asks whether
their direction still feels valid — mirror, not compass.

- Preferences are deterministic: a documented triad mapping (gut → direct/
  higher-friction, heart → warm/drift-sensitive, head → reflective/question-led)
  produces defaults for the six fields (coaching_frequency, coaching_style,
  misalignment_threshold, friction_tolerance, prefer_questions_over_directives,
  time_of_day_preference). PUT overrides; regenerate re-derives.
- CheckinCoach (app/services/coaching.py): Anthropic-backed; writes a check-in
  that quotes the person's goals back and asks if the direction still holds.
- Endpoints (app/routers/coaching.py): GET/PUT/regenerate preferences;
  GET/POST checkins; respond (records still_valid); admin POST /run is the
  weekly batch (due = cadence elapsed + locked profile), intended for a cron.
- Models + migration 005: coaching_preferences (per user) and coaching_checkin.
- Frontend: coaching.html (preferences form + check-in feed); linked from
  profile.html.

Tests: 68 passing (added deterministic-preference unit tests and coaching
endpoint/batch tests; run in-container). README updated for Phase 3.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/main.py

@@ -11,7 +11,12 @@ from starlette.middleware.sessions import SessionMiddleware
 from app import models  # noqa: F401 - register ORM models with Base.metadata
 from app.auth import ensure_api_key_admin
 from app.database import AsyncSessionLocal, Base, engine
-from app.routers import activity, auth as auth_router, discovery
+from app.routers import (
+    activity,
+    auth as auth_router,
+    coaching,
+    discovery,
+)
 from app.routers.activity import prune_old_activity
 from app.tracking import ActivityTrackingMiddleware
 
@@ -64,6 +69,7 @@ app.add_middleware(
 app.include_router(auth_router.router)
 app.include_router(activity.router)
 app.include_router(discovery.router)
+app.include_router(coaching.router)
 app.mount("/static", StaticFiles(directory=STATIC_DIR), name="static")