Add NFO scan endpoint and fix scheduler test payload

- Implement /api/nfo/scan endpoint returning scan results
- Fix Robot Framework scheduler test: use Evaluate+json.loads instead of Create Dictionary for nested data
- Remove completed task docs

tests/robot/api/scheduler.robot

@@ -32,12 +32,7 @@ Get Scheduler Config
 
 Update Scheduler Config
     [Documentation]    Update scheduler settings and verify they are persisted.
-    ${payload}=    Create Dictionary
-    ...    enabled=True
-    ...    interval_minutes=120
-    ...    schedule_time=04:30
-    ...    schedule_days=['mon', 'wed', 'fri']
-    ...    auto_download_after_rescan=True
+    ${payload}=    Evaluate    json.loads('''{"enabled": true, "interval_minutes": 120, "schedule_time": "04:30", "schedule_days": ["mon", "wed", "fri"], "auto_download_after_rescan": true}''')    modules=json
     ${resp}=    Update Scheduler Config    ${payload}
     Response Should Have Status    ${resp}    200
     ${saved_time}=    Get JSON Value    ${resp}    $.config.schedule_time