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/styles/theme.css

@@ -613,6 +613,29 @@ button[disabled] {
   color: var(--muted);
   border: 1px solid var(--line);
 }
+.badge-moderator {
+  background: rgba(224, 176, 112, 0.12);
+  color: #e0b070;
+  border: 1px solid rgba(224, 176, 112, 0.4);
+}
+/* Action-type badges for the moderation dashboard. */
+.badge-ban {
+  background: rgba(217, 139, 132, 0.16);
+  color: #d98b84;
+  border: 1px solid rgba(217, 139, 132, 0.4);
+}
+.badge-kick,
+.badge-mute,
+.badge-warn {
+  background: rgba(224, 176, 112, 0.12);
+  color: #e0b070;
+  border: 1px solid rgba(224, 176, 112, 0.4);
+}
+.badge-auto {
+  background: rgba(127, 153, 189, 0.14);
+  color: #9fb0c6;
+  border: 1px solid var(--line);
+}
 .link-accent {
   color: var(--accent);
   text-decoration: none;