fix: prevent duplicate user_ prefix in usernames

- Update user creation logic to strip 'user_' prefix from Clerk ID before generating username
- Change default username pattern from 'user_<clerkId>' to 'user<cleanId>'
- This prevents usernames like 'user_user_35Z...' and creates 'user35Z...' instead
- Apply fix to both userService and reportController
- Add migration script to fix existing duplicate usernames

Example: user_user_35ZFZ... -> user35ZFZ...

server/src/scripts/fixDuplicateUsernames.ts

@@ -0,0 +1,61 @@
+/**
+ * Script to fix duplicate usernames that have the pattern user_user_xxxxx
+ * 
+ * This script updates usernames that were created with the old logic
+ * where we used `user_${clerkId}` and the clerkId already started with 'user_'
+ * 
+ * Usage: npx ts-node src/scripts/fixDuplicateUsernames.ts
+ */
+
+import prisma from '../config/database';
+
+async function fixDuplicateUsernames() {
+  console.log('🔍 Finding users with duplicate username pattern...\n');
+
+  try {
+    // Find all users with usernames starting with 'user_user_'
+    const usersToFix = await prisma.user.findMany({
+      where: {
+        username: {
+          startsWith: 'user_user_',
+        },
+      },
+    });
+
+    console.log(`Found ${usersToFix.length} users to fix\n`);
+
+    if (usersToFix.length === 0) {
+      console.log('✅ No users need fixing!');
+      return;
+    }
+
+    // Fix each user
+    for (const user of usersToFix) {
+      const oldUsername = user.username;
+      
+      // Remove the duplicate 'user_' prefix
+      const newUsername = oldUsername.replace(/^user_user_/, 'user');
+      
+      console.log(`Updating user ${user.id}:`);
+      console.log(`  Old: ${oldUsername}`);
+      console.log(`  New: ${newUsername}`);
+
+      await prisma.user.update({
+        where: { id: user.id },
+        data: { username: newUsername },
+      });
+
+      console.log('  ✅ Updated\n');
+    }
+
+    console.log(`\n✅ Successfully fixed ${usersToFix.length} usernames!`);
+  } catch (error) {
+    console.error('❌ Error fixing usernames:', error);
+    throw error;
+  } finally {
+    await prisma.$disconnect();
+  }
+}
+
+// Run the script
+fixDuplicateUsernames();