fix: address a11y code review findings

Bugs fixed:
- Space key was hijacked in tag input when a suggestion was
  highlighted, preventing users from typing spaces. Removed
  Space as a selection key (Enter is sufficient per combobox
  pattern).
- ArrowUp was clamped to index 0, making it impossible to
  deselect all suggestions and return to free typing. Now
  allows arrowing back to -1 which clears aria-activedescendant.

Cleanup:
- Remove dead inline onkeydown handlers from tag suggestion
  <li> elements (tabindex="-1" means they never receive focus,
  so the handlers never fire; the global keydown listener in
  app.js handles keyboard navigation).
- Add outline to aria-selected="true" state for visual parity
  with hover (keyboard users now see the same indicator).
- Announce "Ingen forslag" in live region when suggestions are
  empty (screen readers previously got silence).
- Add responsive table wrapper to admin tags and admin requests
  tables (was only on admin users).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/static/css/style.css

@@ -164,6 +164,8 @@
 
 .tag-suggestion[aria-selected="true"] {
     background: var(--pico-primary-focus);
+    outline: 2px solid var(--pico-primary);
+    outline-offset: -2px;
 }
 
 /* Fave detail actions */