Add automatic role assignment for new and existing users

- Implemented auto-assignment of the 'private' role for new users upon first login, ensuring they have access to products.
- Added a safety check to assign the 'private' role to existing users without roles during login.
- Updated relevant documentation to reflect these changes in role management and visibility patterns.

server/api/auth/login.post.ts

@@ -63,6 +63,11 @@ export default defineEventHandler(async (event) => {
         .returning()
 
       user = newUser
+
+      // Auto-assign 'private' role on first login
+      await assignRoleToUser(newUser.id, 'private', {
+        adminNotes: 'Auto-assigned on first login',
+      })
     } else {
       // Update last login timestamp
       await db
@@ -71,6 +76,14 @@ export default defineEventHandler(async (event) => {
           updatedAt: new Date(),
         })
         .where(eq(users.id, user.id))
+
+      // Safety check: If existing user has no roles, assign 'private' role
+      const userRoleCodes = await getUserApprovedRoleCodes(user.id)
+      if (userRoleCodes.length === 0) {
+        await assignRoleToUser(user.id, 'private', {
+          adminNotes: 'Auto-assigned for existing user without roles',
+        })
+      }
     }
 
     // 6. Create encrypted session