feat: redesign mod detail page layout

[ruxwez]

Description

This PR redesigns the mod detail page to address the issues reported in #806:

• Smaller image: image max height is now constrained with max-h-80 (up to max-h-112 on larger screens) and an aspect-ratio is applied to maintain proportions, preventing images from taking up the entire viewport.
• Install button repositioned: the install button now lives in the same column as the mod title and description, making it far more visible and accessible without needing to scroll past the image.

Changes

• ✅ Redesigned layout to 2 columns (lg:grid-cols-[3fr_2fr]) on large screens: image on the left, info on the right.
• ✅ Image now has a constrained max height (max-h-80/96/112) and aspect-[1.85/1] for a much more contained size.
• ✅ Install/Uninstall buttons moved to the info column, right alongside the mod title.
• ✅ Improved author section: badge with GitHub icon + mod version (v{version}).
• ✅ Creation/update dates now use calendar icons (CalendarIcon, CalendarClockIcon).
• ✅ New SVG icon components: CalendarIcon.astro and CalendarClockIcon.astro.

Before / After

Before

After

How to test

1. Navigate to any mod detail page, e.g.: /mods/906c6915-5677-48ff-9bfc-096a02a72379/
2. Verify the image is smaller and no longer takes up the full width.
3. Verify the "Install" button appears next to the title and is easily visible.
4. Check that the 2-column layout kicks in at lg breakpoint (≥1024px).
5. Verify the calendar icons and author/version badge render correctly.

Related issues

Closes #806