Polish /report-bug's visual design and refine bug report semantics

Design pass on the bug report page, staying inside the site's existing
design system (tokens, IBM Plex Sans, card/badge/pill components, stroke
icon set) rather than introducing a new one:
- A slim top bar (brand mark + back-to-home pill button + language switcher)
  replaces the bare floating heading, so the page reads as part of the
  product instead of an orphaned form.
- The "write in English" notice moves inside the form card, right above the
  field it applies to, and switches from the amber "needs attention" tone to
  an accent-tinted info tone, so it doesn't visually collide with the
  bug-status badges' own use of amber for "not read yet".
- "Your reports" is promoted to a proper labeled section with a cleaner row
  layout (truncated description with a title tooltip, compact date).
- A character counter on the description field.
- The back-to-home control is now a bordered pill with an arrow icon instead
  of a bare text link with a hardcoded "←", which also meant dropping that
  hardcoded arrow from all 7 translations.

Also, two content refinements based on feedback:
- Max description length dropped from 5000 to 2000 characters, enforced on
  both the textarea and the API's Pydantic validator.
- The "read" status is relabeled from a passive "read"/"letta" to an active
  "acknowledged"/"presa in carico" (and each other language's own equivalent
  helpdesk term) — it communicates a team is on it, not just that someone
  glanced at it. Only the label changed; the underlying "read" status value
  in the API/DB is untouched.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/static/admin.js

@@ -346,7 +346,7 @@ async function loadAuditLog() {
   }
 }
 
-const BUG_REPORT_STATUS_LABELS = { open: 'Da leggere', read: 'Letta', resolved: 'Risolta' };
+const BUG_REPORT_STATUS_LABELS = { open: 'Da leggere', read: 'Presa in carico', resolved: 'Risolta' };
 
 function bugReportBadge(status) {
   return `<span class="badge bug-status-${escapeHtml(status)}">${escapeHtml(BUG_REPORT_STATUS_LABELS[status] || status)}</span>`;
@@ -366,7 +366,7 @@ async function loadBugReports() {
         <td>
           ${bugReportBadge(r.status)}
           <div class="bug-actions">
-            ${r.status === 'open' ? `<button class="secondary" onclick="setBugReportStatus(${r.id}, 'read', this)">Segna come letta</button>` : ''}
+            ${r.status === 'open' ? `<button class="secondary" onclick="setBugReportStatus(${r.id}, 'read', this)">Segna come presa in carico</button>` : ''}
             ${r.status !== 'resolved' ? `<button class="secondary" onclick="setBugReportStatus(${r.id}, 'resolved', this)">Segna come risolta</button>` : ''}
             ${r.status !== 'open' ? `<button class="secondary" onclick="setBugReportStatus(${r.id}, 'open', this)">Riapri</button>` : ''}
           </div>