feat: analytics parity — tool cost, date ranges, budgets, query explorer, replay, snapshots (v2.4.0)

Analytics parity phases 2–7 (docs/plans/analytics-parity/), built on
138e706 and ported onto v2.3.1:
- Cost by AI tool (?tool= on cost/analytics/stats/workflows, by_tool,
  Codex fast/priority and flex tiers, agenthub_cost_usd_total{tool,model})
- Date ranges (from/to) on cost/analytics/workflows; Analytics range select
  with Today / This week (Monday) / This month (1st) / 7d / 30d / 90d / All /
  Custom; workflow filters carried into workflow-stats.js (read worker)
- Budgets and cost alerts as alert rule types (alert_rules rebuilt without
  its rule_type CHECK), GET /api/budgets/status, rule preview, spend pace,
  status-bar budget chip; rules stay editable in place
- Query Explorer (/query, allowlisted sort, CSV/JSON export) and scheduled
  reports (report_definitions/report_runs, Settings → Reports)
- Session Replay tab and immutable snapshots (session_snapshots, /snapshot/:token)
- Remote Codex sync, push ingest with a hashed token, privacy redaction and
  ignored folders (Settings → Data), Cursor sessions (no cost)
- Read-only MCP server, statusline, Grafana/Prometheus files

Also: resizable sidebar, pet run/wave animations, the workspace home keeps a
half-typed prompt, and the pre-commit hook runs only the related tests for a
small commit.

client/src/App.tsx

@@ -82,6 +82,12 @@ const SettingsHub = lazy(() =>
 const SessionDetail = lazy(() =>
   import("./pages/SessionDetail").then((m) => ({ default: m.SessionDetail }))
 );
+const SnapshotView = lazy(() =>
+  import("./pages/SnapshotView").then((m) => ({ default: m.SnapshotView }))
+);
+const QueryExplorer = lazy(() =>
+  import("./pages/QueryExplorer").then((m) => ({ default: m.QueryExplorer }))
+);
 
 function PageFallback() {
   const { t } = useTranslation();
@@ -158,6 +164,22 @@ export default function App() {
                 </Page>
               }
             />
+            <Route
+              path="snapshot/:token"
+              element={
+                <Page>
+                  <SnapshotView />
+                </Page>
+              }
+            />
+            <Route
+              path="query"
+              element={
+                <Page>
+                  <QueryExplorer />
+                </Page>
+              }
+            />
             <Route path="activity" element={<Navigate to="/sessions?view=events" replace />} />
             <Route
               path="workflows"