fix: add fallback registries and improve deployment reliability

- Add fallback to official npm/PyPI registries when Chinese mirrors fail
- Fix dev workflow mirror host (127.0.0.1 -> 100.78.131.124)
- Add error handling and diagnostics to build steps
- Fix iPhone UI: make download/delete buttons always visible on mobile
- Add .dockerignore to reduce build context size

dashboard/frontend/src/routes/Files.svelte

@@ -135,7 +135,7 @@
             </span>
           {/if}
           <span class="text-xs text-surface-400 text-right">{e.is_dir ? "—" : formatSize(e.size)}</span>
-          <div class="flex items-center justify-end gap-1 opacity-0 group-hover:opacity-100 transition-opacity">
+          <div class="flex items-center justify-end gap-1 opacity-100 md:opacity-0 md:group-hover:opacity-100 transition-opacity">
             {#if !e.is_dir}
               <button onclick={() => handleDownload(e.name)} class="text-[11px] text-primary-500 hover:text-primary-700 font-medium transition-colors">DL</button>
             {/if}