Polish dashboard frontend: spacing, copy, resilience

- Increase content padding (p-7→p-8) and table cell padding (px-4→px-5,
  py-3→py-4 for data rows) across capsules, keys, and snapshots pages
- Improve animation performance: wrenn-glow uses opacity instead of
  box-shadow (compositor-only, no paint cost)
- Add prefers-reduced-motion media query covering inline style animations
- Fix OAuth error display on login page (read ?error= param on mount)
- Harden clipboard copy with try-catch and toast fallback
- Improve empty state copy, dialog microcopy, and error messages
- Add retry button to error banners on keys page
- Replace "All systems operational" footer bar with a clean 1px divider
- Fix text truncation on long capsule/snapshot names (min-w-0 + truncate)

frontend/src/routes/auth/github/callback/+page.svelte

@@ -24,5 +24,5 @@
 </script>
 
 <div class="flex min-h-screen items-center justify-center">
-	<p class="text-[13px] text-[var(--color-text-secondary)]">Signing you in...</p>
+	<p class="text-ui text-[var(--color-text-secondary)]">Signing you in...</p>
 </div>