feat(webui): add Install to Disk page

Expose the existing bee-install script through the web UI:
- platform/install.go: remove USB exclusion, add SizeBytes/MountedParts
  fields, add MinInstallBytes()/DiskWarnings() safety checks (size,
  mounted partitions, toram+low-RAM warning)
- webui: add GET /api/install/disks, POST /api/install/run,
  GET /api/install/stream endpoints
- webui: add Install to Disk page with disk table, warning badges,
  device-name confirmation gate, SSE progress terminal, reboot button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/jobs.go

@@ -76,6 +76,13 @@ func (m *jobManager) create(id string) *jobState {
 	return j
 }
 
+// isDone returns true if the job has finished (either successfully or with error).
+func (j *jobState) isDone() bool {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	return j.done
+}
+
 func (m *jobManager) get(id string) (*jobState, bool) {
 	m.mu.Lock()
 	defer m.mu.Unlock()