Phase 3.2 WS2: Mitra request activity log + control center page

- DB migration: add active_session_count column + mitra_notified index
- Constants: add MISSED to NotificationResponse
- Pairing service: record active_session_count on notification creation,
  use MISSED (not IGNORED) when another mitra accepts first
- New mitra-activity.service.js: getMitraActivityLog (paginated),
  getMitraActivitySummary (per-mitra aggregates with acceptance rate)
- New mitra-activity.routes.js: GET /internal/mitra-activity/log,
  GET /internal/mitra-activity/summary
- Control center: new MitraActivityPage with summary table + detail log,
  filters (mitra, date range), color-coded response types, pagination
- Register route in App.jsx, add "Aktivitas Mitra" nav link in Layout

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/services/mitra-activity.service.js

@@ -0,0 +1,75 @@
+import { getDb } from '../db/client.js'
+
+const sql = getDb()
+
+export const getMitraActivityLog = async ({ mitra_id, date_from, date_to, page = 1, limit = 20 } = {}) => {
+  const offset = (page - 1) * limit
+  const conditions = []
+
+  if (mitra_id) conditions.push(sql`crn.mitra_id = ${mitra_id}`)
+  if (date_from) conditions.push(sql`crn.notified_at >= ${date_from}`)
+  if (date_to) conditions.push(sql`crn.notified_at <= ${date_to}`)
+
+  const where = conditions.length > 0
+    ? sql`WHERE ${conditions.reduce((a, b) => sql`${a} AND ${b}`)}`
+    : sql``
+
+  const items = await sql`
+    SELECT crn.id, crn.session_id, crn.mitra_id, crn.response,
+      crn.notified_at, crn.responded_at, crn.active_session_count,
+      m.display_name AS mitra_display_name,
+      CASE WHEN crn.responded_at IS NOT NULL
+        THEN EXTRACT(EPOCH FROM (crn.responded_at - crn.notified_at))::int
+        ELSE NULL
+      END AS response_time_seconds
+    FROM chat_request_notifications crn
+    INNER JOIN mitras m ON m.id = crn.mitra_id
+    ${where}
+    ORDER BY crn.notified_at DESC
+    LIMIT ${limit} OFFSET ${offset}
+  `
+
+  const [{ count }] = await sql`
+    SELECT COUNT(*) FROM chat_request_notifications crn ${where}
+  `
+
+  return { items, total: Number(count), page, limit }
+}
+
+export const getMitraActivitySummary = async ({ mitra_id, date_from, date_to } = {}) => {
+  const conditions = []
+
+  if (mitra_id) conditions.push(sql`crn.mitra_id = ${mitra_id}`)
+  if (date_from) conditions.push(sql`crn.notified_at >= ${date_from}`)
+  if (date_to) conditions.push(sql`crn.notified_at <= ${date_to}`)
+
+  const where = conditions.length > 0
+    ? sql`WHERE ${conditions.reduce((a, b) => sql`${a} AND ${b}`)}`
+    : sql``
+
+  const summaries = await sql`
+    SELECT crn.mitra_id,
+      m.display_name AS mitra_display_name,
+      COUNT(*)::int AS total_requests,
+      COUNT(*) FILTER (WHERE crn.response = 'accepted')::int AS accepted_count,
+      COUNT(*) FILTER (WHERE crn.response = 'declined')::int AS rejected_count,
+      COUNT(*) FILTER (WHERE crn.response = 'missed')::int AS missed_count,
+      COUNT(*) FILTER (WHERE crn.response = 'ignored')::int AS ignored_count,
+      ROUND(
+        100.0 * COUNT(*) FILTER (WHERE crn.response = 'accepted') / NULLIF(COUNT(*), 0), 1
+      ) AS acceptance_rate,
+      AVG(
+        CASE WHEN crn.responded_at IS NOT NULL
+          THEN EXTRACT(EPOCH FROM (crn.responded_at - crn.notified_at))
+          ELSE NULL
+        END
+      )::numeric(10,1) AS avg_response_time_seconds
+    FROM chat_request_notifications crn
+    INNER JOIN mitras m ON m.id = crn.mitra_id
+    ${where}
+    GROUP BY crn.mitra_id, m.display_name
+    ORDER BY acceptance_rate DESC NULLS LAST
+  `
+
+  return summaries
+}