docs: api comments say what the endpoints do, not how they came to be (#6277)

Rewrites the internal/api comment blocks to rule 32: task, milestone and
rule ids gone, the stories behind them restated as the constraint they
left, stale references corrected (the stream secret is wired from config,
the timezone handler already refreshes the scheduler, the Android app is
the native client, the design docs cited are not in the repo). Also
rewraps comment lines over 80 columns left by the earlier batches.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/events_stream.go

@@ -1,6 +1,6 @@
 // Live event stream — Server-Sent Events at GET /api/events/stream.
 //
-// Clients (today: Flutter) subscribe to be notified of state changes
+// The web app and the Android app subscribe to be notified of state changes
 // elsewhere in the system (likes, request status flips, quarantine
 // resolutions, scan progress, playlist mutations) so static screens
 // can invalidate cached data without explicit user action.