fix: improve text contrast in filter labels and update login button text

- Change login button text from "Log In" to "Login"
- Update filter labels (Kategorie, Icon, Tags, Saison, Favoriten) to use darker color (nord2) in light mode for better readability
- Improve placeholder text contrast in filter inputs by using lighter shade (nord4)
- Maintain light color scheme (nord6) for filter labels in dark mode

src/lib/components/UserHeader.svelte

@@ -147,5 +147,5 @@ h2 + p{
 		</div>
 	</button>
 {:else}
-	<a class=entry href=/login>Log In</a>
+	<a class=entry href=/login>Login</a>
 {/if}