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/likes.go

@@ -16,9 +16,9 @@ import (
 
 // logLikeChange writes a library_changes row for a like / unlike. Best-
 // effort: a failure here means the next sync may miss the row, but the
-// HTTP response still succeeds. Cheap consequence — operator's other
-// device will see the like once it manually pulls or once a future
-// like/unlike on the same entity emits a fresh log row.
+// HTTP response still succeeds. Cheap consequence — the user's other
+// device sees the like once it manually pulls, or once a later like/unlike
+// on the same entity emits a fresh log row.
 func (h *handlers) logLikeChange(r *http.Request, et syncpkg.EntityType, userID, entityID pgtype.UUID, op syncpkg.Op) {
 	if err := syncpkg.LogChange(r.Context(), h.pool, et,
 		syncpkg.EncodeLikeID(syncpkg.FormatUUID(userID), syncpkg.FormatUUID(entityID)), op); err != nil {
@@ -60,7 +60,7 @@ func (h *handlers) handleLikeTrack(w http.ResponseWriter, r *http.Request) {
 	if slices.Contains(liked, id) {
 		_ = playevents.CaptureContextualLikeIfPlaying(r.Context(), q, user.ID, id, h.logger)
 	}
-	// The like is on the song (M498 #5438): every copy it reached changes on
+	// The like is on the song: every copy it reached changes on
 	// the client too.
 	for _, t := range withTrack(id, liked) {
 		h.logLikeChange(r, syncpkg.EntityLikeTrack, user.ID, t, syncpkg.OpUpsert)