fix: email XSS sanitization, bulk invite concurrency, error handling (code review batch 2)

- Add escapeHtml() helper and apply to all user-supplied variables in 20+ HTML email templates
- Auto-escape in sectionTitle() and statCard() helpers for defense-in-depth
- Replace 5 instances of incomplete manual escaping with escapeHtml()
- Refactor bulkInviteTeamMembers: batch all DB writes in $transaction, then send emails via Promise.allSettled with concurrency pool of 10
- Fix inner catch block in award-eligibility-job.ts to capture its own error variable

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

src/server/routers/round.ts

@@ -1264,33 +1264,53 @@ export const roundRouter = router({
       const expiryHours = await getInviteExpiryHours(ctx.prisma as unknown as import('@prisma/client').PrismaClient)
       const expiryMs = expiryHours * 60 * 60 * 1000
 
-      let invited = 0
       let skipped = 0
       let failed = 0
 
+      // Phase 1: Batch all DB writes — generate tokens and update users
+      const toInvite: Array<{ id: string; email: string; name: string | null; role: string; token: string }> = []
       for (const [, user] of users) {
         if (user.status === 'ACTIVE' || user.status === 'INVITED') {
           skipped++
           continue
         }
+        toInvite.push({ ...user, token: generateInviteToken() })
+      }
 
-        try {
-          const token = generateInviteToken()
-          await ctx.prisma.user.update({
-            where: { id: user.id },
-            data: {
-              status: 'INVITED',
-              inviteToken: token,
-              inviteTokenExpiresAt: new Date(Date.now() + expiryMs),
-            },
+      if (toInvite.length > 0) {
+        await ctx.prisma.$transaction(
+          toInvite.map((u) =>
+            ctx.prisma.user.update({
+              where: { id: u.id },
+              data: {
+                status: 'INVITED',
+                inviteToken: u.token,
+                inviteTokenExpiresAt: new Date(Date.now() + expiryMs),
+              },
+            })
+          )
+        )
+      }
+
+      // Phase 2: Send emails with concurrency pool of 10
+      const CONCURRENCY = 10
+      let invited = 0
+
+      for (let i = 0; i < toInvite.length; i += CONCURRENCY) {
+        const batch = toInvite.slice(i, i + CONCURRENCY)
+        const results = await Promise.allSettled(
+          batch.map((u) => {
+            const inviteUrl = `${baseUrl}/accept-invite?token=${u.token}`
+            return sendInvitationEmail(u.email, u.name, inviteUrl, u.role, expiryHours)
           })
-
-          const inviteUrl = `${baseUrl}/accept-invite?token=${token}`
-          await sendInvitationEmail(user.email, user.name, inviteUrl, user.role, expiryHours)
-          invited++
-        } catch (err) {
-          console.error(`[bulkInviteTeamMembers] Failed for ${user.email}:`, err)
-          failed++
+        )
+        for (const result of results) {
+          if (result.status === 'fulfilled') {
+            invited++
+          } else {
+            console.error('[bulkInviteTeamMembers] Email send failed:', result.reason)
+            failed++
+          }
         }
       }