perf(database): index PersonalAccessToken.userId so token lookups stop seq-scanning

Both PAT-by-user lookups (userId + revokedAt is null, and userId + name)
had no index on userId and seq-scanned the whole table, reading ~44k-47k
rows to return ~1. userId is also an unindexed foreign key. Add @@index
([userId]); a user owns few PATs so the single-column index serves both
query shapes.

Seeded local EXPLAIN (50k rows): Seq Scan -> Index Scan on both queries,
shared buffers 689 pages -> 3.

Author: ericallam

.server-changes/index-personal-access-token-user-id.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: improvement
+---
+
+Speed up personal access token lookups by indexing them on their owner

internal-packages/database/prisma/migrations/20260812140000_add_personal_access_token_user_id_index/migration.sql

@@ -0,0 +1 @@
+CREATE INDEX CONCURRENTLY IF NOT EXISTS "PersonalAccessToken_userId_idx" ON "public"."PersonalAccessToken"("userId");

internal-packages/database/prisma/schema.prisma

@@ -155,6 +155,8 @@ model PersonalAccessToken {
   updatedAt DateTime @updatedAt
 
   authorizationCodes AuthorizationCode[]
+
+  @@index([userId])
 }
 
 enum OrganizationAccessTokenType {