feat(scheduler): add cron-style scheduled jobs (backend)

Adds a saved/named scheduling layer on top of Codeman's existing session
primitives. Distinct from the legacy run-now ScheduledRun concept.

- types/scheduler.ts: ScheduledJob + ScheduledJobRun
- state-store: persist scheduledJobs/scheduledJobRuns in ~/.codeman/state.json
- scheduler/scheduler-time.ts: pure once/interval/daily/weekly next-run math
- scheduler/scheduler-service.ts: CRUD, Run Now, due-checker tick, run history;
  reuses SessionPort (create -> start -> writeViaMux) for launches
- web/routes/scheduler-routes.ts: /api/scheduler/jobs CRUD + run + history
- web/schemas.ts: zod validation with schedule-type-aware refinements
- web/sse-events.ts: scheduler:* events
- server.ts: wire service into route context + 30s background tick loop
- test/scheduler-time.test.ts: 14 unit tests for next-run calculations

Phase 1 discovery recorded in SCHEDULER_DISCOVERY.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rp7JhmQXcYJhmxFMdZuuah

src/web/routes/index.ts

@@ -7,6 +7,7 @@ export { registerTeamRoutes } from './team-routes.js';
 export { registerMuxRoutes } from './mux-routes.js';
 export { registerFileRoutes } from './file-routes.js';
 export { registerScheduledRoutes } from './scheduled-routes.js';
+export { registerSchedulerRoutes } from './scheduler-routes.js';
 export { registerSystemRoutes } from './system-routes.js';
 export { registerHookEventRoutes } from './hook-event-routes.js';
 export { registerStatusTelemetryRoutes } from './status-telemetry-routes.js';