fix: prevent register page from forcing scroll on short viewports

The .register section had min-height: 80vh, which combined with the
marketing layout's header and footer pushed total page height past 100vh
on shorter viewports, causing the page to scroll even when the card
content fit comfortably.

Make the marketing main element a flex column so the register section
can flex: 1 to fill remaining space without overflowing the viewport.

Closes #30

Author: dobby-coder[bot]

src/routes/(marketing)/+layout.svelte

@@ -20,5 +20,7 @@
 	main {
 		flex: 1;
 		width: 100%;
+		display: flex;
+		flex-direction: column;
 	}
 </style>

src/routes/(marketing)/register/+page.svelte

@@ -234,7 +234,7 @@
 			var(--pg-soft-background) 0%,
 			var(--pg-general-background) 100%
 		);
-		min-height: 80vh;
+		flex: 1;
 	}
 
 	.register-card {