feat: backdated reported date for old active tickets

Wahab can now enter historical tickets that keep their true reported date:

- Add nullable tickets.reported_at (DateTime) via alembic d5e0f2a1c3b4;
  backfill existing rows from created_at so nothing shows empty.
- TicketCreate.reported_at (optional) is persisted by create_ticket and
  defaults to now when omitted, so existing create behavior is unchanged.
- New-issue form gains a 'Reported Date' date picker (defaults to today,
  past dates allowed, future blocked) and sends reported_at in the payload.
- List and detail pages show 'Reported' next to 'Created' (date-only,
  labeled) so backdated tickets are obvious; SLA deadline is unchanged and
  still runs from creation time so backfilling never instantly breaches.
- Tests: backdated create persists + is exposed on list/detail; omitted
  reported_at defaults to now; SLA window unchanged; full datetime round trip.

app/templates/tickets/detail.html

@@ -23,7 +23,11 @@
                             <span class="px-3 py-1 rounded-full text-sm font-medium" :class="statusClass(ticket.status)" x-text="ticket.status"></span>
                             <span class="px-3 py-1 rounded text-sm font-medium" :class="priorityClass(ticket.priority)" x-text="priorityBadge(ticket.priority)"></span>
                         </div>
-                        <p class="text-gray-500 mt-1">Created <span x-text="formatDate(ticket.created_at)"></span></p>
+                        <p class="text-gray-500 mt-1">Created <span x-text="formatDate(ticket.created_at)"></span>
+                            <template x-if="ticket.reported_at && formatDateShort(ticket.reported_at) !== formatDateShort(ticket.created_at)">
+                                <span> · Reported <span class="font-medium text-gray-600" x-text="formatDateShort(ticket.reported_at)"></span></span>
+                            </template>
+                        </p>
                     </div>
                     <div class="flex items-center space-x-2">
                         <button @click="showStatusModal = true" class="px-4 py-2 bg-denya-600 text-white rounded-lg hover:bg-denya-700 transition text-sm font-medium">Update Status</button>
@@ -129,6 +133,10 @@
                                 <dt class="text-sm text-gray-500">Reported Via</dt>
                                 <dd class="text-sm font-medium text-gray-900 capitalize" x-text="ticket.reported_via || '—'"></dd>
                             </div>
+                            <div class="flex justify-between">
+                                <dt class="text-sm text-gray-500">Reported</dt>
+                                <dd class="text-sm font-medium text-gray-900" x-text="ticket.reported_at ? formatDateShort(ticket.reported_at) : formatDateShort(ticket.created_at)"></dd>
+                            </div>
                             <div class="flex justify-between">
                                 <dt class="text-sm text-gray-500">Priority</dt>
                                 <dd><span class="px-2 py-0.5 rounded text-xs font-medium" :class="priorityClass(ticket.priority)" x-text="priorityBadge(ticket.priority)"></span></dd>