Add multi-mode support for authentication: login, register, and forgot password

Refactored login component to support three modes: login, registration, and password recovery. Introduced new UI and validation for each mode. Updated styles to accommodate mode-specific layouts.

src/styles/components.css

@@ -716,3 +716,30 @@ textarea {
     max-width: 100%;
   }
 }
+
+/* Auth helpers: links below forms */
+.auth-links {
+  margin-top: 12px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  flex-wrap: wrap;
+}
+
+.auth-links .divider {
+  color: var(--gray);
+}
+
+.link {
+  background: none;
+  border: none;
+  padding: 0;
+  color: var(--primary);
+  cursor: pointer;
+  font-weight: 600;
+}
+
+.link:hover {
+  text-decoration: underline;
+}