feat: filter and search by tag

internal/storage/sqlite.go

@@ -155,7 +155,13 @@ func (s *SQLiteStorage) Search(query string) []*note.Note {
         SELECT id, path, title, content, updated_at, size, published
         FROM notes
         WHERE lower(content) LIKE lower(?)
-    `, pattern)
+        OR id IN (
+            SELECT nt.note_id
+            FROM note_tags nt
+            JOIN tags t ON t.id = nt.tag_id
+            WHERE lower(t.name) LIKE lower(?)
+        )
+    `, pattern, pattern)
 	if err != nil {
 		return []*note.Note{}
 	}

internal/storage/sqlite_test.go

@@ -187,3 +187,27 @@ func TestSQLiteStorage_Tags(t *testing.T) {
 		t.Fatalf("expected remaining tag rust, got %+v", tags)
 	}
 }
+
+func TestSQLiteStorage_SearchByTag(t *testing.T) {
+	st := newSQLiteStorage(t)
+
+	ts := time.Date(2026, 2, 3, 12, 0, 0, 0, time.UTC)
+	if err := st.Create(sampleNote("n1", "notes/alpha.md", "Alpha", "no match", ts)); err != nil {
+		t.Fatalf("create note: %v", err)
+	}
+	if err := st.Create(sampleNote("n2", "notes/beta.md", "Beta", "content", ts)); err != nil {
+		t.Fatalf("create note: %v", err)
+	}
+
+	if err := st.AddTag("n2", "Go"); err != nil {
+		t.Fatalf("add tag: %v", err)
+	}
+
+	results := st.Search("go")
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	if results[0].ID != "n2" {
+		t.Fatalf("expected tag match to be n2")
+	}
+}

internal/storage/storage.go

@@ -67,13 +67,25 @@ func (ns *NoteStorage) Search(query string) []*note.Note {
 	for _, note := range ns.Index {
 		lowContent := strings.ToLower(string(note.Content))
 		lowQuery := strings.ToLower(query)
-		if strings.Contains(lowContent, lowQuery) {
+		if strings.Contains(lowContent, lowQuery) || tagsContain(note.Tags, lowQuery) {
 			results = append(results, note)
 		}
 	}
 	return results
 }
 
+func tagsContain(tags []string, query string) bool {
+	if query == "" {
+		return false
+	}
+	for _, tag := range tags {
+		if strings.Contains(strings.ToLower(tag), query) {
+			return true
+		}
+	}
+	return false
+}
+
 func (ns *NoteStorage) AddTag(noteID, tag string) error {
 	n, ok := ns.Index[noteID]
 	if !ok {

internal/storage/storage_test.go

@@ -51,3 +51,20 @@ func TestNoteStorageGetUpdate(t *testing.T) {
 		t.Errorf("Updating a note should reflect it in storage. Wanted '%s', got '%s'\n", n1.Content, nn2.Content)
 	}
 }
+
+func TestNoteStorageSearch_Tags(t *testing.T) {
+	ns = NewNoteStorage()
+
+	n := note.NewNote()
+	n.Path = "note3.md"
+	n.ID = note.GenerateNoteID(n.Path)
+	n.Content = "no tag here"
+	n.Tags = []string{"devops", "go"}
+
+	ns.Create(n)
+
+	results := ns.Search("go")
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+}