fix(mentor): unbreak the mentor pipeline end-to-end

Adding the MENTOR role from /admin/members/[id] only updated React state — the
AlertDialog "Add role" confirmation never called the server, so prod ended up
with zero users in MENTOR roles[] and /admin/mentors showed "No mentors yet".
The dialog now awaits updateUser.mutateAsync({ roles }) before closing.

Other corrections in the same area:

- DialogContent uses flex flex-col with max-h-[90vh] overflow-y-auto so tall
  modals (e.g. Add Project to Round) scroll internally instead of overflowing
  past their own rounded background.
- getProjectsNeedingMentor now matches autoAssignBulkForRound exactly: both
  filter mentorAssignments by droppedAt: null and require
  finalistConfirmation: CONFIRMED, so the toolbar count never exceeds what
  auto-fill actually processes. The toolbar surfaces hasNoMentors /
  hasNoEligible / count / all-assigned as distinct states instead of one
  misleading "All eligible projects have a mentor" line.
- New per-team table (MentoringProjectsTable) replaces ProjectStatesTable on
  the Projects tab of MENTORING rounds. Lists every project with its active
  mentors (multi-mentor aware), filter pills, search, finalist-confirmation
  badge, and a per-row link to /admin/projects/[id]/mentor for assigning.
- Applicant team page now lists ALL active mentors (PR8 Task 7) instead of
  just mentorAssignments[0].
- Hard guard in src/lib/email.ts short-circuits sendEmail when NODE_ENV=test
  or VITEST=true so test runs can never emit real notifications again.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/server/routers/mentor.ts

@@ -818,7 +818,7 @@ export const mentorRouter = router({
         where: {
           roundId: input.roundId,
           project: {
-            mentorAssignments: { none: {} },
+            mentorAssignments: { none: { droppedAt: null } },
             // Only assign mentors to projects whose team has confirmed they will
             // attend the grand finale. This skips PENDING/DECLINED/EXPIRED/SUPERSEDED
             // confirmations and any project without a confirmation row at all.