feat(ui): add scan progress and error reporting to UI (#4094)

* feat(scanner): add LastScanError tracking to scanner status

- Introduced LastScanErrorKey constant for error tracking.
- Updated StatusInfo struct to include LastError field.
- Modified scanner logic to store and retrieve last scan error.
- Enhanced ScanStatus response to include error information.
- Updated UI components to display last scan error when applicable.
- Added tests to verify last scan error functionality.

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(scanner): enhance scan status with type and elapsed time tracking

- Added LastScanTypeKey and LastScanStartTimeKey constants for tracking scan type and start time.
- Updated StatusInfo struct to include ScanType and ElapsedTime fields.
- Implemented getScanInfo method to retrieve scan type, elapsed time, and last error.
- Modified scanner logic to store scan type and start time during scans.
- Enhanced ScanStatus response and UI components to display scan type and elapsed time.
- Added formatShortDuration utility for better elapsed time representation.
- Updated activity reducer to handle new scan status fields.

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor(tests): consolidate controller status tests into a single file

- Removed the old controller_status_test.go file.
- Merged relevant tests into the new controller_test.go file for better organization and maintainability.
- Ensured all existing test cases for controller status are preserved and functional.

Signed-off-by: Deluan <deluan@navidrome.org>

* Fix formatting issues

* refactor(scanner): update getScanInfo method documentation

---------

Signed-off-by: Deluan <deluan@navidrome.org>

ui/src/reducers/activityReducer.js

@@ -6,15 +6,24 @@ import {
 import config from '../config'
 
 const initialState = {
-  scanStatus: { scanning: false, folderCount: 0, count: 0 },
+  scanStatus: {
+    scanning: false,
+    folderCount: 0,
+    count: 0,
+    error: '',
+    elapsedTime: 0,
+  },
   serverStart: { version: config.version },
 }
 
 export const activityReducer = (previousState = initialState, payload) => {
   const { type, data } = payload
+
   switch (type) {
-    case EVENT_SCAN_STATUS:
-      return { ...previousState, scanStatus: data }
+    case EVENT_SCAN_STATUS: {
+      const elapsedTime = Number(data.elapsedTime) || 0
+      return { ...previousState, scanStatus: { ...data, elapsedTime } }
+    }
     case EVENT_SERVER_START:
       return {
         ...previousState,