feat(17-05): implement serve and schedule commands replacing stubs

- cmd/serve.go: starts scheduler, optionally starts Telegram bot with --telegram flag
- cmd/schedule.go: add/list/remove/run subcommands for scheduled scan job CRUD
- pkg/scheduler/: gocron v2 based scheduler with DB-backed jobs and scan execution
- pkg/storage/scheduled_jobs.go: scheduled_jobs table CRUD with tests
- Remove serve and schedule stubs from cmd/stubs.go

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/stubs.go

@@ -25,16 +25,8 @@ var verifyCmd = &cobra.Command{
 
 // keysCmd is implemented in cmd/keys.go (Phase 6).
 
-var serveCmd = &cobra.Command{
-	Use:   "serve",
-	Short: "Start the web dashboard (Phase 18)",
-	RunE:  notImplemented("serve", "Phase 18"),
-}
+// serveCmd is implemented in cmd/serve.go (Phase 17).
 
 // dorksCmd is implemented in cmd/dorks.go (Phase 8).
 
-var scheduleCmd = &cobra.Command{
-	Use:   "schedule",
-	Short: "Manage scheduled recurring scans (Phase 17)",
-	RunE:  notImplemented("schedule", "Phase 17"),
-}
+// scheduleCmd is implemented in cmd/schedule.go (Phase 17).