feat(phase1): add image storage utilities

- Create backend/services/image_storage.py with 4 core functions:
  - sanitize_filename(): remove unsafe chars, limit to 255 chars, convert to lowercase
  - get_unique_filename(): handle collisions with UUID suffix (format: {name}_{uuid8}_{variant}.jpg)
  - ensure_image_directories(): create /images/ root and category subdirs on startup
  - save_image(): save bytes to /images/{category}/{filename}, returns relative path
- Create comprehensive test suite (22 tests) covering all functionality
- Integrate ensure_image_directories() into FastAPI startup event
- Directory structure: /images/{category}/{filename}
- Collision handling: auto-suffix with UUID if filename exists
- All tests passing, pathlib.Path for safe operations

venv/lib/python3.12/site-packages/apscheduler/schedulers/qt.py

@@ -0,0 +1,44 @@
+from importlib import import_module
+from itertools import product
+
+from apscheduler.schedulers.base import BaseScheduler
+
+for version, pkgname in product(range(6, 1, -1), ("PySide", "PyQt")):
+    try:
+        qtcore = import_module(pkgname + str(version) + ".QtCore")
+    except ImportError:
+        pass
+    else:
+        QTimer = qtcore.QTimer
+        break
+else:
+    raise ImportError("QtScheduler requires either PySide/PyQt (v6 to v2) installed")
+
+
+class QtScheduler(BaseScheduler):
+    """A scheduler that runs in a Qt event loop."""
+
+    _timer = None
+
+    def shutdown(self, *args, **kwargs):
+        super().shutdown(*args, **kwargs)
+        self._stop_timer()
+
+    def _start_timer(self, wait_seconds):
+        self._stop_timer()
+        if wait_seconds is not None:
+            wait_time = min(int(wait_seconds * 1000), 2147483647)
+            self._timer = QTimer.singleShot(wait_time, self._process_jobs)
+
+    def _stop_timer(self):
+        if self._timer:
+            if self._timer.isActive():
+                self._timer.stop()
+            del self._timer
+
+    def wakeup(self):
+        self._start_timer(0)
+
+    def _process_jobs(self):
+        wait_seconds = super()._process_jobs()
+        self._start_timer(wait_seconds)