Add missing database indexes for FK lookups and audit queries

Type(categoryId), Item(typeId), Attachment(uploadedById), and
AuditLog(ticketId, createdAt) were missing indexes for their
primary query patterns.

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

server/prisma/schema.prisma

@@ -57,6 +57,7 @@ model Type {
   tickets    Ticket[]
 
   @@unique([categoryId, name])
+  @@index([categoryId])
 }
 
 model Item {
@@ -67,6 +68,7 @@ model Item {
   tickets Ticket[]
 
   @@unique([typeId, name])
+  @@index([typeId])
 }
 
 model Ticket {
@@ -141,6 +143,7 @@ model Attachment {
 
   @@index([ticketId])
   @@index([commentId])
+  @@index([uploadedById])
 }
 
 model Webhook {
@@ -195,4 +198,6 @@ model AuditLog {
 
   ticket Ticket @relation(fields: [ticketId], references: [id], onDelete: Cascade)
   user   User   @relation(fields: [userId], references: [id])
+
+  @@index([ticketId, createdAt])
 }