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/app.css

@@ -100,9 +100,9 @@
 	--color-border-hover: var(--nord3);
 
 	/* Link Colors */
-	--color-link: var(--nord11);
+	--color-link: var(--nord10);
 	--color-link-visited: var(--nord15);
-	--color-link-hover: var(--color-accent-hover);
+	--color-link-hover: var(--nord9);
 
 	/* Status Colors */
 	--color-success: var(--nord14);
@@ -168,9 +168,9 @@
 		--color-border-hover: var(--nord3);
 
 		/* Link Colors */
-		--color-link: #d07179;
+		--color-link: var(--nord8);
 		--color-link-visited: #c89fb6;
-		--color-link-hover: var(--color-accent-hover);
+		--color-link-hover: var(--nord7);
 	}
 }