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/admin_scan.go

@@ -76,8 +76,8 @@ type scanTriggerResp struct {
 // handleTriggerScan implements POST /api/admin/scan/run.
 // Returns 202 on success, 409 if a scan is already in flight (and not stale),
 // 500 on DB errors. The lazy reaper inside library.TryStartScan handles
-// stale (>1h) in-flight rows automatically — the operator no longer needs
-// to manually clear stuck rows after a server crash.
+// stale (>1h) in-flight rows automatically, so a row left stuck by a
+// server crash needs no manual clearing.
 func (h *handlers) handleTriggerScan(w http.ResponseWriter, _ *http.Request) {
 	bgCtx := context.Background()
 	started, existing, err := library.TryStartScan(