feat(comments): add comment/ticket system across all entity pages

Add CommentSection component for inline comments on entity detail pages
(machines, pieces, composants, products, categories, skeleton types).
Add dedicated /comments page with filters, pagination and clickable links.
Add unresolved count badge on avatar and in profile dropdown.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/pages/machine/[id].vue

@@ -108,6 +108,16 @@
           @edit-piece="d.editPiece"
           @custom-field-update="d.updatePieceCustomField"
         />
+
+        <!-- Comments -->
+        <div class="mt-4">
+          <CommentSection
+            entity-type="machine"
+            :entity-id="String(machineId)"
+            :entity-name="d.machine.value?.name"
+            show-resolved
+          />
+        </div>
       </template>
 
       <template v-else>