feat(tools): harden scheduler speed limiter logs

Modernize the Tools release surfaces for the cross-platform re-release checklist.

- make Speed Limiter presets unit-aware and persist custom removable quick presets

- keep diagnostic logging opt-in on clean installs and honor the saved log state on startup

- stage Scheduler enablement edits without discarding unsaved draft changes

- extend persisted settings and bindings for log opt-in and speed preset state

Verification:

- npm run build

- npm test -- --run src/store/useDownloadStore.test.ts

- cargo test --lib

- cargo test settings --lib

src/store/useDownloadStore.test.ts

@@ -29,6 +29,8 @@ vi.mock('./useSettingsStore', () => ({
       proxyMode: 'none',
       siteLogins: [],
       globalSpeedLimit: '',
+      speedLimitPresetValues: [1, 5, 10],
+      logsEnabled: false,
       perServerConnections: 16,
       customUserAgent: '',
       maxAutomaticRetries: 3,