Location filter for queue and auth fixes (Issue #220)

Features:
- Add location filter for "Any {Model}" queue assignments
- Queue items can target a specific location (e.g., "Any X1C in Workshop")
- Location dropdown filter on Queue page to view jobs by location
- Scheduler considers location when assigning model-based jobs

Closes #220

.gitignore

@@ -58,3 +58,6 @@ firmware/
 node_modules/
 
 data/
+
+# JWT secret file (should be in data dir, but protect project root too)
+.jwt_secret