feat(dashcam): mobile layout fix + optional hw-encode conversion on import

- yaris.css: on mobile (<576px) hide file/size/date/upload cols, show
  filename inside thumb cell, icon-only buttons, dash-actions-td nowrap
- local-videos.js: filename in thumb cell for mobile; Converting badge with
  spinner; auto-refresh every 10s while any file is converting
- app_video.py: CONVERT_SETTING, is_convert_enabled(), queue_convert(),
  _convert_bg() — h264_v4l2m2m + aac faststart, deletes original on success
- app_dash.py: call queue_convert() after each successful copy on import
- app_settings.py: expose video_convert_enabled in get/save settings
- settings.html: toggle for 'Convert imported videos for web playback'

Co-authored-by: Copilot <[email protected]>

static/js/settings.js

@@ -15,6 +15,7 @@ let initialUplinkStatusLoaded = false;
 const fields = {
     dashcamUpload: document.getElementById('dashcam-upload-enabled'),
     retention: document.getElementById('retention-days'),
+    videoConvert: document.getElementById('video-convert-enabled'),
     cellularEnabled: document.getElementById('cellular-enabled'),
     cellularApn: document.getElementById('cellular-apn'),
     ntfyEnabled: document.getElementById('ntfy-enabled'),
@@ -80,6 +81,7 @@ function populate(settings) {
     const thresholds = settings.alert_thresholds;
     fields.dashcamUpload.checked = settings.dashcam_upload_enabled;
     fields.retention.value = settings.local_video_retention_days;
+    fields.videoConvert.checked = settings.video_convert_enabled;
     fields.cellularEnabled.checked = settings.cellular_enabled;
     fields.cellularApn.value = settings.cellular_apn;
     fields.ntfyEnabled.checked = settings.ntfy_enabled;
@@ -105,6 +107,7 @@ function payload() {
     return {
         dashcam_upload_enabled: fields.dashcamUpload.checked,
         local_video_retention_days: Number(fields.retention.value),
+        video_convert_enabled: fields.videoConvert.checked,
         cellular_enabled: fields.cellularEnabled.checked,
         cellular_apn: fields.cellularApn.value,
         ntfy_enabled: fields.ntfyEnabled.checked,