test: boost server test coverage to 80%+ across all packages

Add comprehensive tests for db, storage, updater, and ws packages
covering edge cases, error paths, and voice handler functions.
New test files for attachment queries and WebSocket coverage boost.

Server/storage/storage_test.go

@@ -387,3 +387,90 @@ func TestSave_EmptyFileAllowed(t *testing.T) {
 		t.Errorf("Save(empty) = %v, want nil", err)
 	}
 }
+
+// ─── New edge cases ──────────────────────────────────────────────────────────
+
+func TestNew_CreatesDirectory(t *testing.T) {
+	tmpDir := t.TempDir()
+	newDir := filepath.Join(tmpDir, "nested", "storage")
+
+	s, err := storage.New(newDir, 10)
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+	if s == nil {
+		t.Fatal("New returned nil")
+	}
+
+	// Directory should exist.
+	info, statErr := os.Stat(newDir)
+	if statErr != nil {
+		t.Fatalf("directory not created: %v", statErr)
+	}
+	if !info.IsDir() {
+		t.Error("expected directory, got file")
+	}
+}
+
+// ─── Save large file ────────────────────────────────────────────────────────
+
+func TestSave_ExceedsMaxSize(t *testing.T) {
+	tmpDir := t.TempDir()
+	// 1 MB max.
+	s, err := storage.New(tmpDir, 1)
+	if err != nil {
+		t.Fatalf("New: %v", err)
+	}
+
+	// Create reader with >1MB of data.
+	bigData := bytes.Repeat([]byte("x"), 1024*1024+100)
+	err = s.Save("big-file", bytes.NewReader(bigData))
+	if err == nil {
+		t.Error("Save should reject file exceeding max size")
+	}
+
+	// File should be removed.
+	if _, statErr := os.Stat(filepath.Join(tmpDir, "big-file")); !os.IsNotExist(statErr) {
+		t.Error("oversized file should be removed after rejection")
+	}
+}
+
+func TestSave_ReadError(t *testing.T) {
+	s := newTestStorage(t)
+	err := s.Save("read-err", &failReader{})
+	if err == nil {
+		t.Error("Save with failing reader should return error")
+	}
+}
+
+type failReader struct{}
+
+func (f *failReader) Read([]byte) (int, error) {
+	return 0, errors.New("simulated read error")
+}
+
+// ─── resolvedPath edge case (via Save with dot prefix) ──────────────────────
+
+func TestSave_HiddenFilename(t *testing.T) {
+	s := newTestStorage(t)
+	err := s.Save(".hidden", strings.NewReader("data"))
+	if err == nil {
+		t.Error("Save should reject hidden filenames starting with '.'")
+	}
+}
+
+func TestOpen_NotFound(t *testing.T) {
+	s := newTestStorage(t)
+	_, err := s.Open("nonexistent-file")
+	if err == nil {
+		t.Error("Open should return error for nonexistent file")
+	}
+}
+
+func TestDelete_NotFound(t *testing.T) {
+	s := newTestStorage(t)
+	err := s.Delete("nonexistent-file")
+	if err == nil {
+		t.Error("Delete should return error for nonexistent file")
+	}
+}