feat(US-1011): Add cost budget tracking

- Add BudgetSettings to FeatureSettings (token/cost limits, warning threshold)
- Add budget metrics API endpoint with monthly projections
- Create BudgetCard dashboard component with progress bars and status
- Add budget settings to Settings > Data tab
- Calculate burn rate (tokens/day average) and projected monthly usage
- Color coding: green (<60%), yellow (60-80%), red (>80%)
- Warning when projected usage exceeds budget limit

Features:
- Monthly token limit setting
- Monthly cost limit setting (USD)
- Warning threshold configuration
- Used/Budget progress bar with color indicators
- Projected end-of-month usage
- Daily burn rate display

.veritas-kanban/telemetry/events-2026-01-28.ndjson

@@ -1035,3 +1035,4 @@
 {"type":"task.status_changed","taskId":"task_20260128_hul7-q","project":"veritas-kanban","status":"in-progress","previousStatus":"todo","id":"evt_WQWsGmzLqxyp","timestamp":"2026-01-28T14:05:59.881Z"}
 {"type":"task.status_changed","taskId":"task_20260128_PNPYo1","project":"veritas-kanban","status":"done","previousStatus":"in-progress","id":"evt_c4ps4FT6x136","timestamp":"2026-01-28T14:08:10.123Z"}
 {"type":"task.status_changed","taskId":"task_20260128_V0MVwS","project":"veritas-kanban","status":"in-progress","previousStatus":"todo","id":"evt_Im1OUzfDaHcm","timestamp":"2026-01-28T14:10:44.392Z"}
+{"type":"task.status_changed","taskId":"task_20260128_hul7-q","project":"veritas-kanban","status":"done","previousStatus":"in-progress","id":"evt_iQck1GWDFbr-","timestamp":"2026-01-28T14:11:00.382Z"}

server/.veritas-kanban/activity.json

@@ -1,4 +1,15 @@
 [
+  {
+    "id": "activity_1769609460386_6n876xgld",
+    "type": "status_changed",
+    "taskId": "task_20260128_hul7-q",
+    "taskTitle": "US-1305: Status history log",
+    "details": {
+      "from": "in-progress",
+      "status": "done"
+    },
+    "timestamp": "2026-01-28T14:11:00.386Z"
+  },
   {
     "id": "activity_1769609444392_cqzd626r4",
     "type": "status_changed",