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/api/library_sync_test.go

@@ -41,9 +41,8 @@ func TestLibrarySync_AfterArtistUpsert_ReturnsHydratedPayload(t *testing.T) {
 	truncateLibrary(t, pool)
 	u := seedUser(t, pool, "alice", "x", false)
 
-	// Seed an artist + write a change row in the same tx — that's the
-	// invariant the scanner wiring (Task 5) will enforce, and the
-	// handler relies on.
+	// Seed an artist + write a change row in the same tx — the invariant
+	// library writes keep, and the handler relies on.
 	ctx := context.Background()
 	tx, err := pool.Begin(ctx)
 	if err != nil {
@@ -122,8 +121,8 @@ func TestLibrarySync_DeleteIsReflected(t *testing.T) {
 	u := seedUser(t, pool, "alice", "x", false)
 
 	// Just write a delete change row directly (no underlying mutation).
-	// Scanner wiring (Task 5) is what couples real deletes to LogChange;
-	// here we test the handler reflects what's in the log.
+	// Library writes couple real deletes to LogChange; here we test the
+	// handler reflects what's in the log.
 	ctx := context.Background()
 	tx, _ := pool.Begin(ctx)
 	_ = sync.LogChange(ctx, tx, sync.EntityArtist, "deadbeef-dead-beef-dead-beefdeadbeef", sync.OpDelete)