feat: M1 — LinUCB bandit, RemotePolicy, Web Push, event bus

ML serving:
- LinUCB contextual bandit (disjoint, d=5 features: hour_sin/cos, is_overdue, task_age, priority)
- /score endpoint replaces stub random; /reward endpoint for online learning
- Per-user model state persisted to disk as JSON (survives restarts)
- venv at ml/serving/.venv; start with pnpm dev from ml/serving

Recommender:
- Todoist fetch now extracts features (is_overdue, task_age_days, priority)
- RemotePolicy calls ml/serving with 3s timeout; falls back to RandomPolicy
- Reward sent to /reward on feedback (done=+1, snooze=0, dismiss=-1)

Web Push:
- VAPID keys in config; push_subscriptions table in DB
- POST/DELETE /api/push/subscribe; GET /api/push/vapid-public-key
- Service worker (public/sw.js): push → showNotification, notificationclick → focus/open
- "notify me" button on tip page; registers SW + subscribes on permission grant

Event bus:
- services/api/src/events/bus.ts: typed EventEmitter wrapper
- Subjects: signals.tip.served, signals.tip.feedback, signals.task.synced
- Same publish/subscribe API NATS JetStream will implement — swap is mechanical

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

services/api/src/index.ts

@@ -9,6 +9,7 @@ import { authRouter } from './routes/auth.js';
 import { integrationsRouter } from './routes/integrations.js';
 import { recommenderRouter } from './routes/recommender.js';
 import { userRouter } from './routes/user.js';
+import { pushRouter } from './routes/push.js';
 import { mkdir } from 'fs/promises';
 import { dirname } from 'path';
 
@@ -33,6 +34,7 @@ app.use('/api/auth', authRouter);
 app.use('/api/integrations', integrationsRouter);
 app.use('/api', recommenderRouter);
 app.use('/api/user', userRouter);
+app.use('/api/push', pushRouter);
 
 app.listen(config.PORT, () => {
   console.log(`oO API listening on http://localhost:${config.PORT}`);