fix(dashboard): F-U-009 add download link + copy-id button per file row

Listing showed name/content-type/size/created/id; only mutation was
Delete. No download link, no copy-id button (the UUID was rendered
unclickable), no preview, no metadata refresh. Operators had to use
the admin API directly.

- Add api.files.downloadUrl(slug, collection, id) helper that builds
  the admin GET URL. The anchor uses HTML `download` so the browser
  saves with the original filename.
- Add a ⧉ copy-id button next to the UUID column using
  navigator.clipboard.writeText. Silently no-ops where the browser
  doesn't expose clipboard (plain-http LAN).
- Preview / metadata-refresh are deferred to a UI overhaul.

AUDIT.md anchor: F-U-009 (partial — download + copy; preview deferred).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/routes/apps/[slug]/files/+page.svelte

@@ -91,6 +91,12 @@
 		return new Date(iso).toLocaleString();
 	}
 
+	// F-U-009: best-effort clipboard copy; silently no-ops where the
+	// browser doesn't expose navigator.clipboard (e.g. plain-http LAN).
+	function copyToClipboard(text: string) {
+		void navigator.clipboard?.writeText(text);
+	}
+
 	function fmtSize(bytes: number): string {
 		if (bytes < 1024) return `${bytes} B`;
 		if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
@@ -180,8 +186,25 @@
 							<td><code>{f.content_type}</code></td>
 							<td>{fmtSize(f.size)}</td>
 							<td>{fmtTime(f.created_at)}</td>
-							<td class="mono small">{f.id}</td>
+							<td class="mono small">
+								{f.id}
+								<button
+									type="button"
+									class="copy-btn"
+									title="Copy ID"
+									onclick={() => copyToClipboard(f.id)}
+								>
+									⧉
+								</button>
+							</td>
 							<td>
+								<a
+									class="secondary"
+									href={api.files.downloadUrl(slug, activeCollection, f.id)}
+									download={f.name}
+								>
+									Download
+								</a>
 								<button type="button" class="danger" onclick={() => (fileToRemove = f)}>
 									Delete
 								</button>