Add student profile page with password change

- New page /profile: shows name/email and password change form
- Uses authClient.changePassword (current + new + confirm)
- Student name in header is now a link to /profile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/(student)/layout.tsx

@@ -44,7 +44,9 @@ export default async function StudentLayout({ children }: { children: React.Reac
           {schoolName}
         </Link>
         <div className="flex items-center gap-4">
-          <span className="text-sm" style={{ color: "var(--muted-foreground)" }}>{session.user.name}</span>
+          <Link href="/profile" className="text-sm hover:underline" style={{ color: "var(--muted-foreground)" }}>
+            {session.user.name}
+          </Link>
           <LogoutButton />
         </div>
       </header>