feat: improve accessibility and update color scheme based on PageSpeed insights

- Add aria-labels to icon-only links (add button, edit button, logo, nav toggle)
- Add main landmark element for better page structure
- Fix heading hierarchy on recipe pages (h1 → h2 → h3 progression)
- Add role="status" to loading placeholders to allow aria-label usage
- Update link colors from red to blue for better contrast in both light and dark modes
- Change hover colors from orange/red to light blue across all interactive elements
- Reduce font size of section labels (Season, Keywords) while maintaining semantic structure

These changes address PageSpeed accessibility recommendations including low-contrast text,
missing accessible names, prohibited ARIA attributes, missing landmarks, and improper
heading order.

src/lib/components/LazyCategory.svelte

@@ -58,6 +58,7 @@
 	<div
 		bind:this={containerRef}
 		style="height: {estimatedHeight}px; min-height: {estimatedHeight}px;"
+		role="status"
 		aria-label="Loading {title}"
 	>
 		<!-- Empty placeholder - IntersectionObserver will trigger when this enters viewport -->