Add repair notes journal with running feed, visibility, and status tagging

New repair_note table for timestamped journal entries on tickets. Each
note captures author, content, visibility (internal or customer-facing),
and the ticket status at time of writing. Notes display as a running
feed on the ticket detail page with newest first. Internal notes have
a lock icon, customer-visible notes highlighted in blue. Supports add
and delete with appropriate permission gating.

packages/backend/src/db/migrations/meta/_journal.json

@@ -127,6 +127,13 @@
       "when": 1774770000000,
       "tag": "0017_repair_in_transit_status",
       "breakpoints": true
+    },
+    {
+      "idx": 18,
+      "version": "7",
+      "when": 1774780000000,
+      "tag": "0018_repair_notes",
+      "breakpoints": true
     }
   ]
 }