feat(team): add team analytics dashboard

Add a team document-usage dashboard at /t/:teamUrl/analytics for team admins and managers,
behind the NEXT_PUBLIC_FEATURE_TEAM_ANALYTICS_ENABLED rollout flag (enabled by default, set to
"false" to gate it off).

Backend:
- getTeamAnalytics Kysely query over team-produced documents across all folders, with exact
  COUNT(*) (no STATS_COUNT_CAP). Each metric uses its own date axis: Sent/Draft/Pending by
  createdAt, Completed by Envelope.completedAt, Declined by the DOCUMENT_RECIPIENT_REJECTED
  audit-log timestamp.
- resolveAnalyticsPeriod turns calendar presets into half-open [start, end) ranges in the
  viewer's timezone, falling back to UTC.
- team.getAnalytics tRPC route gated to ADMIN/MANAGER.

Frontend:
- Standalone /t/:teamUrl/analytics route whose loader gates the flag and role, silently
  redirecting members to documents.
- Headline metrics and compact stat tiles, a member multiselect filter, a calendar-preset
  period selector, and an empty state.
- Role- and flag-gated nav entries in the desktop and mobile navigation.

Tests:
- Unit tests for the period resolver (timezone and preset boundaries).
- Integration/E2E tests for the query semantics (date axes, audit-log decline, all-folders
  aggregation, sender attribution), access control, filters and the empty state.

packages/trpc/server/team-router/router.ts

@@ -16,6 +16,7 @@ import { findTeamGroupsRoute } from './find-team-groups';
 import { findTeamMembersRoute } from './find-team-members';
 import { findTeamsRoute } from './find-teams';
 import { getTeamRoute } from './get-team';
+import { getTeamAnalyticsRoute } from './get-team-analytics';
 import { getTeamMembersRoute } from './get-team-members';
 import {
   ZCreateTeamEmailVerificationMutationSchema,
@@ -32,6 +33,7 @@ import { updateTeamSettingsRoute } from './update-team-settings';
 export const teamRouter = router({
   find: findTeamsRoute,
   get: getTeamRoute,
+  getAnalytics: getTeamAnalyticsRoute,
   create: createTeamRoute,
   update: updateTeamRoute,
   delete: deleteTeamRoute,