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.

alembic/versions/d5e0f2a1c3b4_tickets_reported_at.py

@@ -0,0 +1,47 @@
+"""tickets.reported_at column — original reported date for backdated tickets
+
+Revision ID: d5e0f2a1c3b4
+Revises: c4e8f1a2d3b4
+Create Date: 2026-08-03 00:00:00.000000
+
+Backdated-ticket support (Wahab demo): one schema change.
+
+* Add ``tickets.reported_at`` (nullable DateTime) so historical/backfilled
+  tickets keep their true report date instead of inheriting today's
+  ``created_at``.
+* Backfill existing rows with their ``created_at`` value so no ticket shows
+  an empty reported date after the upgrade. The service layer also defaults
+  new tickets without a ``reported_at`` to now, so the column is effectively
+  always populated from here on.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'd5e0f2a1c3b4'
+down_revision: Union[str, Sequence[str], None] = 'c4e8f1a2d3b4'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Add tickets.reported_at (nullable) and backfill from created_at."""
+    op.add_column(
+        'tickets',
+        sa.Column(
+            'reported_at',
+            sa.DateTime(),
+            nullable=True,
+            comment='Original reported date; backdated/backfilled tickets keep their true report date',
+        ),
+    )
+    # Backfill: every existing ticket was reported when it was created.
+    op.execute('UPDATE tickets SET reported_at = created_at WHERE reported_at IS NULL')
+
+
+def downgrade() -> None:
+    """Drop tickets.reported_at."""
+    op.drop_column('tickets', 'reported_at')