Fix missing image alt text and intrinsic dimensions

[LukasWallrich]

Why this needs addressing

The live homepage contains 24 images; 3 news thumbnails have no alt attribute. Nearly all sampled images also lack intrinsic width/height attributes. This is a confirmed accessibility gap and can contribute to layout shifts while images load.

Requested change

• Give meaningful content images concise, context-appropriate alt text.
• Use alt="" only for genuinely decorative images.
• Add intrinsic dimensions or an equivalent aspect-ratio reservation for stable images, especially above the fold and repeated card components.
• Audit shared image partials as well as homepage content so the fix is template-level.

Acceptance criteria

• No indexable/content image is missing an alt decision (meaningful alt or deliberate empty alt).
• Representative pages reserve image space before loading and show no avoidable layout shift.
• Existing responsive sizing and lazy loading continue to work.