Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

templates/register.html

@@ -0,0 +1,25 @@
+{% extends "base.html" %}
+
+{% block title %}Register{% endblock %}
+
+{% block content %}
+<div class="container">
+    <h1>Register</h1>
+    <form id="register-form">
+        <div class="form-group">
+            <label for="username">Username:</label>
+            <input type="text" id="username" name="username" required>
+        </div>
+        <div class="form-group">
+            <label for="email">Email:</label>
+            <input type="email" id="email" name="email" required>
+        </div>
+        <div class="form-group">
+            <label for="password">Password:</label>
+            <input type="password" id="password" name="password" required>
+        </div>
+        <button type="submit">Register</button>
+    </form>
+    <p>Already have an account? <a href="/login">Login here</a></p>
+</div>
+{% endblock %}