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-3.11.2.dist-info/entry_points.txt

@@ -0,0 +1,25 @@
+[apscheduler.executors]
+asyncio = apscheduler.executors.asyncio:AsyncIOExecutor
+debug = apscheduler.executors.debug:DebugExecutor
+gevent = apscheduler.executors.gevent:GeventExecutor
+processpool = apscheduler.executors.pool:ProcessPoolExecutor
+threadpool = apscheduler.executors.pool:ThreadPoolExecutor
+tornado = apscheduler.executors.tornado:TornadoExecutor
+twisted = apscheduler.executors.twisted:TwistedExecutor
+
+[apscheduler.jobstores]
+etcd = apscheduler.jobstores.etcd:EtcdJobStore
+memory = apscheduler.jobstores.memory:MemoryJobStore
+mongodb = apscheduler.jobstores.mongodb:MongoDBJobStore
+redis = apscheduler.jobstores.redis:RedisJobStore
+rethinkdb = apscheduler.jobstores.rethinkdb:RethinkDBJobStore
+sqlalchemy = apscheduler.jobstores.sqlalchemy:SQLAlchemyJobStore
+zookeeper = apscheduler.jobstores.zookeeper:ZooKeeperJobStore
+
+[apscheduler.triggers]
+and = apscheduler.triggers.combining:AndTrigger
+calendarinterval = apscheduler.triggers.calendarinterval:CalendarIntervalTrigger
+cron = apscheduler.triggers.cron:CronTrigger
+date = apscheduler.triggers.date:DateTrigger
+interval = apscheduler.triggers.interval:IntervalTrigger
+or = apscheduler.triggers.combining:OrTrigger