Fix duplicate accessibility IDs in repeatable blocks

[lbbbboom]

What changed

This PR fixes duplicate and missing accessibility-related IDs in repeatable theme blocks and snippets.

• Makes contact form field IDs unique per form instance.
• Adds a concrete email error ID for contact form aria-describedby.
• Makes popup link dialog heading IDs unique per block instance.
• Makes review star SVG definition IDs unique per block instance.
• Makes blog comment form error IDs unique and ensures the email field references an existing error element.

Why

Several repeatable blocks used fixed DOM IDs or referenced IDs that may not exist. When multiple instances render on the same page, this can produce duplicate IDs or broken aria-labelledby / aria-describedby associations.

Validation

shopify theme check

Result:

327 files inspected with no offenses found.

[shopify-shipitnext]

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