docs: update docs for cron, shortener, CI

Add !cron section to USAGE.md and CHEATSHEET.md.
Mark cron, URL shortener, CI complete in ROADMAP.md and TODO.md.
New sprint in TASKS.md.

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

TODO.md

@@ -4,8 +4,8 @@
 
 - [ ] Multi-server support (per-server config, shared plugins)
 - [ ] Stable plugin API (versioned, breaking change policy)
-- [ ] Paste overflow (auto-paste long output to FlaskPaste)
-- [ ] URL shortener integration (shorten URLs in alerts/output)
+- [x] Paste overflow (auto-paste long output to FlaskPaste)
+- [x] URL shortener integration (shorten URLs in subscription announcements)
 - [ ] Webhook listener (HTTP endpoint for push events to channels)
 - [ ] Granular ACLs (per-command: trusted, operator, admin)
 
@@ -80,9 +80,9 @@ is preserved in git history for reference.
 
 - [x] `paste` -- manual paste to FlaskPaste
 - [x] `shorten` -- manual URL shortening
-- [ ] `cron` -- scheduled bot commands on a timer
+- [x] `cron` -- scheduled bot commands on a timer
 
 ## Testing
 
 - [x] Plugin command unit tests (encode, hash, dns, cidr, defang)
-- [ ] CI pipeline
+- [x] CI pipeline (Gitea Actions)