Add moderation dashboard, user history & notes (Phase 6a)

Surface the Discord bot's moderation data on the admin panel: a read-only
staff dashboard over the existing mod_actions log, per-user history, staff
notes, and a new moderator role. No bot changes.

Schema
- users.role ENUM gains 'moderator' (CREATE + idempotent ALTER for existing DBs)
- new server-owned mod_notes table (staff_only/admin_only visibility)

Server
- model/moderation: read mod_actions via the shared pool (documented read-only
  cross of the bot/server ownership boundary), correlate accounts through
  user_identities (provider='discord'), flag automated actions via
  staff_user_id === bot_config.application_id; pure reshaping helpers isolated
  in moderation.pure.js so they unit-test without opening a DB pool
- model/modNotes: list/add with role-gated admin_only visibility
- admin/moderation.controller + routes under /api/v1/admin/moderation/* gated by
  requireRole('admin','moderator'); admin_only note writes require admin
- allow assigning 'moderator' in the user create/update validators

Client
- /admin/moderation overview (window tiles, type-filterable recent feed, user
  lookup) and /user/:discordId history (tabs + notes with add-note)
- RoleGate; AdminLayout filters nav and confines moderators to their section
- moderator badge + action-type/auto badges

Deferred (see plan): 6b bot event capture (joins/leaves/filter/spam), 6c appeals
(needs public accounts), 6d /internal/mod-reverse bot reversal callback.

Verified: 116 server unit tests, client build, DB-backed model smoke, full
HTTP/RBAC e2e, and a browser click-through of the dashboard.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019rao86n5cXpwAyjdBFEshV

client/src/api/client.js

@@ -120,6 +120,30 @@ export const api = {
     updateUser: (id, data) => req(`/admin/users/${id}`, { method: 'PUT', body: data }),
     deleteUser: (id) => req(`/admin/users/${id}`, { method: 'DELETE' }),
 
+    // ----- moderation dashboard (admin + moderator) -----
+    modSummary: () => req('/admin/moderation/stats/summary'),
+    modRecent: (params = {}) => {
+      const qs = new URLSearchParams()
+      if (params.type) qs.set('type', params.type)
+      if (params.limit) qs.set('limit', params.limit)
+      if (params.offset) qs.set('offset', params.offset)
+      const s = qs.toString()
+      return req(`/admin/moderation/recent${s ? `?${s}` : ''}`)
+    },
+    modSearch: (q) => req(`/admin/moderation/search?q=${encodeURIComponent(q)}`),
+    modUser: (discordId) => req(`/admin/moderation/user/${discordId}`),
+    modUserActions: (discordId, params = {}) => {
+      const qs = new URLSearchParams()
+      if (params.type) qs.set('type', params.type)
+      if (params.limit) qs.set('limit', params.limit)
+      if (params.offset) qs.set('offset', params.offset)
+      const s = qs.toString()
+      return req(`/admin/moderation/user/${discordId}/actions${s ? `?${s}` : ''}`)
+    },
+    modUserNotes: (discordId) => req(`/admin/moderation/user/${discordId}/notes`),
+    addModNote: (discordId, data) =>
+      req(`/admin/moderation/user/${discordId}/notes`, { method: 'POST', body: data }),
+
     // ----- account security (self-service 2FA) -----
     getAccount: () => req('/admin/account'),
     totpSetup: () => req('/admin/account/totp/setup', { method: 'POST' }),