feat: round user tracker + fix INVITED status not updating on login

- Replace Semi-Finalist Tracker with Round User Tracker on dashboard
- New getRoundUserStats query: round-aware account activation stats
- Round selector dropdown to view any round's passed projects
- sendAccountReminders now accepts optional roundId for scoped reminders
- Fix: signIn callback now sets status=ACTIVE for INVITED users on login
- DB fix: 5 users who logged in via magic link but stayed INVITED → ACTIVE

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/auth.ts

@@ -390,11 +390,21 @@ export const { handlers, auth, signIn, signOut } = NextAuth({
         user.mustSetPassword = dbUser.mustSetPassword || !dbUser.passwordHash
       }
 
-      // Update last login time on actual sign-in
+      // Update last login time on actual sign-in, and activate INVITED users on login
       if (user.email) {
+        const loginUser = await prisma.user.findUnique({
+          where: { email: user.email },
+          select: { status: true },
+        })
         await prisma.user.update({
           where: { email: user.email },
-          data: { lastLoginAt: new Date() },
+          data: {
+            lastLoginAt: new Date(),
+            // If user is still INVITED but successfully logged in, activate them
+            ...(loginUser && loginUser.status === 'INVITED'
+              ? { status: 'ACTIVE' }
+              : {}),
+          },
         }).catch(() => {
           // Ignore errors from updating last login
         })