chore(db): stop wiping databases with an older schema version

All installations are past schema version 2, so the one-time reset is gone;
data is never deleted on start (demo mode still resets). user_version is kept
for future migrations. Legal test uses an in-memory DB (cleanup race).

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

internal/api/server_test.go

@@ -1369,7 +1369,8 @@ func TestFirstBootSetupWithSampleData(t *testing.T) {
 
 // Impressum and Datenschutz must be reachable without login; unset texts stay hidden.
 func TestLegalTextsArePublic(t *testing.T) {
-	dbPath := filepath.Join(t.TempDir(), "legal.db")
+	// In memory: no files the cleanup could race with
+	dbPath := ":memory:"
 	store, err := storage.NewStore(dbPath)
 	if err != nil {
 		t.Fatalf("NewStore: %v", err)