docs: plan-era "v1", "Task N" and "Phase N" wording restated as facts (#6277)

The marker list behind the earlier server and web passes did not catch
"for v1", "Task 5", "Phase 2" or "today: Flutter". Those comments now say
what the code does.

Corrected: coverart said "both v1 providers" ship on. There are four
providers (MBCAA, TheAudioDB, Deezer, Last.fm), and Last.fm, which needs a
key, ships off.

Non-comment tokens unchanged against HEAD: 10 Go files, 7 TS/Svelte files.

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

internal/coverart/provider_theaudiodb.go

@@ -23,8 +23,8 @@ const (
 
 	// theAudioDBMinPeriod enforces TheAudioDB's documented free/test
 	// rate limit (2 req/sec). Patreon supporter keys allow higher
-	// rates; we don't differentiate in v1 — operators with supporter
-	// keys experience the conservative 2 req/sec ceiling.
+	// rates; we don't differentiate — supporter keys get the same
+	// conservative 2 req/sec ceiling.
 	theAudioDBMinPeriod = 500 * time.Millisecond
 
 	// theAudioDBMaxRetries is the number of retry attempts on 429 /