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/types.go

@@ -7,7 +7,7 @@ import (
 )
 
 // LoginRequest is the POST /api/auth/login body. Kept boring on purpose —
-// web and Flutter both send the same payload.
+// web and Android send the same payload.
 type LoginRequest struct {
 	Username string `json:"username"`
 	Password string `json:"password"`
@@ -15,7 +15,8 @@ type LoginRequest struct {
 
 // LoginResponse carries the opaque session token AND the authenticated user
 // so the SPA can hydrate its auth store in one round-trip. The token is also
-// set as a cookie; SPAs ignore the body token, Flutter uses it as bearer.
+// set as a cookie; the SPA ignores the body token, a native client may send
+// it as a bearer.
 type LoginResponse struct {
 	Token string   `json:"token"`
 	User  UserView `json:"user"`
@@ -82,7 +83,7 @@ type TrackRef struct {
 	DiscNumber  int    `json:"disc_number,omitempty"`
 	DurationSec int    `json:"duration_sec"`
 	StreamURL   string `json:"stream_url"`
-	// Unavailable reports that the file is missing from disk (#2704).
+	// Unavailable reports that the file is missing from disk.
 	//
 	// Present on every TrackRef rather than only where it can be true: the
 	// selection surfaces (recommendation, discover, mixes, browse) filter
@@ -99,11 +100,11 @@ type TrackRef struct {
 type ArtistDetail struct {
 	ArtistRef
 	Albums []AlbumRef `json:"albums"`
-	// Genres carried by this artist's tracks, for quick-jump chips (#367).
+	// Genres carried by this artist's tracks, for quick-jump chips.
 	// Always non-nil at JSON so the client can iterate without a null check.
 	Genres []string `json:"genres"`
-	// MBID is the artist's MusicBrainz id, which following is keyed by
-	// (M502 #5520). Empty when the tags never named one.
+	// MBID is the artist's MusicBrainz id, which following is keyed by.
+	// Empty when the tags never named one.
 	MBID string `json:"mbid"`
 }
 
@@ -111,7 +112,7 @@ type ArtistDetail struct {
 type AlbumDetail struct {
 	AlbumRef
 	Tracks []TrackRef `json:"tracks"`
-	// Genres carried by this album's tracks, for quick-jump chips (#367).
+	// Genres carried by this album's tracks, for quick-jump chips.
 	// Derived from the tracks rather than stored on the album, because genre
 	// lives on tracks and an album's tracks can disagree. Non-nil at JSON.
 	Genres []string `json:"genres"`