feat: profile support for independent marker sets

Each profile has its own set of timeline markers, so the same video
can be cut with different settings (e.g. landscape vs portrait) without
markers interfering. Profile selector in the top bar, persisted in
QSettings, stored per-row in the DB.

- Add `profile` column to ProcessedDB schema (migrates existing rows
  to 'default')
- Scope find_similar, get_markers, _get_markers_for by profile
- Add get_profiles() for populating the combo dropdown
- Thread profile through _DBWorker, _after_load, _refresh_markers,
  _on_clip_done, dropEvent, _on_open_files
- Editable profile QComboBox in top bar, refreshed after each export
- 5 new tests for profile isolation and backward compatibility (54 total)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_utils.py

@@ -344,3 +344,71 @@ def test_db_get_group_disabled():
 def test_db_delete_group_disabled():
     db = ProcessedDB("/no/such/directory/8cut.db")
     assert db.delete_group("/out/clip_001.mp4") == []
+
+
+# --- Profiles ---
+
+def test_db_markers_isolated_by_profile():
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        db.add("video.mp4", 10.0, "/out/a_001.mp4", profile="landscape")
+        db.add("video.mp4", 20.0, "/out/b_001.mp4", profile="portrait")
+        land = db.get_markers("video.mp4", profile="landscape")
+        port = db.get_markers("video.mp4", profile="portrait")
+        assert len(land) == 1
+        assert land[0][0] == 10.0
+        assert len(port) == 1
+        assert port[0][0] == 20.0
+    finally:
+        os.unlink(path)
+
+
+def test_db_find_similar_isolated_by_profile():
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        db.add("episode_2160p.mkv", 0.0, "/out/a.mp4", profile="hires")
+        # Same normalized name but different profile → no match
+        assert db.find_similar("episode_1080p.mkv", profile="lores") is None
+        # Same profile → match
+        assert db.find_similar("episode_1080p.mkv", profile="hires") == "episode_2160p.mkv"
+    finally:
+        os.unlink(path)
+
+
+def test_db_get_profiles():
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        assert db.get_profiles() == []
+        db.add("a.mp4", 0.0, "/out/a.mp4", profile="beta")
+        db.add("b.mp4", 0.0, "/out/b.mp4", profile="alpha")
+        db.add("c.mp4", 0.0, "/out/c.mp4", profile="beta")
+        profiles = db.get_profiles()
+        assert profiles == ["alpha", "beta"]
+    finally:
+        os.unlink(path)
+
+
+def test_db_get_profiles_disabled():
+    db = ProcessedDB("/no/such/directory/8cut.db")
+    assert db.get_profiles() == []
+
+
+def test_db_default_profile_backward_compat():
+    """Existing tests pass without explicit profile — defaults to 'default'."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        path = f.name
+    try:
+        db = ProcessedDB(path)
+        db.add("video.mp4", 5.0, "/out/clip.mp4")
+        markers = db.get_markers("video.mp4")  # no profile arg
+        assert len(markers) == 1
+        assert markers[0][0] == 5.0
+        assert db.get_profiles() == ["default"]
+    finally:
+        os.unlink(path)