Updates from Gitea, step 5: the daily check's announcement, the docs, ADR 0009

The announcement was cut at the notification's 48 bytes; it now reads
"v0.11.0 is out: see Settings > Firmware". README: Updates from Gitea
and its limits. ADR 0009: the device trusts the two ISRG roots. R1.md:
what was built and the checks on the device, with what wasn't checked.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/services/update_service.h

@@ -69,6 +69,7 @@ class UpdateService : public Service {
     void requestProbe(const std::string& host, const std::string& path) { probeHost_ = host; probePath_ = path; probeResult_ = "..."; request_ = Request::Probe; }
     std::string probeResult() const { return probeResult_; }
     void damageNextDownload(long cutAfter, long flipAt) { damageCut_ = cutAfter; damageFlip_ = flipAt; }
+    void forgetToday() { store_.putInt("rel_day", 0); nextCheckMs_ = 0; announced_.clear(); }  // the daily check runs at the next tick
 #endif
 
     // The main loop calls this once it has drawn a frame (part of Probation).