refactor(bruno): reorganize file structure from bruno-yaml to flat bruno directory

- Move all files from bruno-yaml/* to bruno/*
- Maintains existing directory structure within categories
- Updates bruno/user/auth files with OAuth2 refresh token flow
- Updates bruno/user/profile files for user profile management
- Adds bruno/dashboard/ directory with dashboard API tests
- Preserves all existing test scenarios and OpenCollection YAML format
- No functional changes - file reorganization only

bruno/user/auth/Register User.yml

@@ -0,0 +1,57 @@
+info:
+  name: Register User
+  type: http
+  seq: 2
+http:
+  method: POST
+  url: '{{base_url}}/api/auth/register'
+  auth: inherit
+  body:
+    type: json
+    jsonBody: "{\n    \"email\": \"testuser@example.com\",\n    \"username\": \"testuser\"\
+      ,\n    \"password\": \"Test@Pass123!\",\n    \"first_name\": \"Test\",\n   \
+      \ \"last_name\": \"User\""
+
+docs: |-
+  ## Register User
+    
+    Creates a new user account with role-based restrictions.
+    
+    **Method:** POST
+    
+    **Endpoint:** /api/auth/register
+    
+     **Request Body:**
+     - `email` (string): Email address
+     - `username` (string): Username
+     - `password` (string): Password
+     - `first_name` (string, optional): First name
+     - `last_name` (string, optional): Last name
+     - `role` (string): User role ("user" or "admin")
+    
+    **Response:**
+     - `token` (string): JWT token
+      - `user` (object): User details
+         - `id` (string): User ID
+         - `email` (string): Email
+         - `username` (string): Username
+     - `theme` (string): User theme preference
+         - `first_name` (string, optional): First name
+         - `last_name` (string, optional): Last name
+         - `role` (string): User role ("user" or "admin")
+    
+    **Status Codes:**
+     - 201: Created
+     - 400: Invalid input data
+     - 403: Forbidden - role-based restrictions apply
+     - 409: User exists
+    
+    **Role Restrictions:**
+     - **First User**: Automatically gets admin role regardless of request
+     - **Existing Admins Present**: Only authenticated admins can create new admin accounts
+     - **No Admins Yet**: Anyone can create first admin (auto-assigned)
+     - **Regular User Creation**: Anyone can create regular user accounts
+     - **Unauthenticated Users**: Can only create first admin, not subsequent admins
+    
+    **Examples:**
+     - First admin creation: `{"email": "admin@example.com", "username": "admin", "password": "password123", "role": "admin"