feat: saved searches (bookmarks)

- Add saved_searches_collection to database.py with index on created_by+created_at
- New routes/saved_searches.py: GET /api/saved-searches, POST, DELETE
- Saved searches are scoped per user (created_by = token sub)
- Mount router in main.py
- Frontend: Save filters button, saved search pills with load/delete
- loadSavedSearches called on initApp
- applySavedSearch restores filters and validates services against current options
- Add CSS for saved-searches row
- Add tests for CRUD, delete 404, and name validation

backend/database.py

@@ -7,6 +7,7 @@ from pymongo import ASCENDING, DESCENDING, TEXT, MongoClient
 client = MongoClient(MONGO_URI or "mongodb://localhost:27017")
 db = client[DB_NAME]
 events_collection = db["events"]
+saved_searches_collection = db["saved_searches"]
 logger = structlog.get_logger("aoc.database")
 
 
@@ -20,6 +21,7 @@ def setup_indexes(max_retries: int = 5, delay: float = 2.0):
             events_collection.create_index([("timestamp", DESCENDING)])
             events_collection.create_index([("service", ASCENDING), ("timestamp", DESCENDING)])
             events_collection.create_index("id")
+            saved_searches_collection.create_index([("created_by", ASCENDING), ("created_at", DESCENDING)])
             events_collection.create_index(
                 [("actor_display", TEXT), ("raw_text", TEXT), ("operation", TEXT)],
                 name="text_search_index",