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.go

@@ -32,7 +32,7 @@ type Provider interface {
 	RequiresAPIKey() bool
 
 	// DefaultEnabled is whether a freshly-installed Minstrel ships
-	// with this provider on. Both v1 providers return true.
+	// with this provider on. Providers that need an API key ship off.
 	DefaultEnabled() bool
 
 	// Configure receives the admin's settings (api_key, enabled
@@ -102,8 +102,8 @@ type ArtistArtProvider interface {
 
 // TestableProvider is an opt-in capability: providers that can answer
 // "is my config working?" without performing a full enrichment cycle.
-// Used by the admin Test-Connection button. v1: both MBCAA and
-// TheAudioDB implement this.
+// Used by the admin Test-Connection button. MBCAA and TheAudioDB
+// implement this.
 type TestableProvider interface {
 	Provider
 	TestConnection(ctx context.Context) error

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 /