Add browser tokens for public link device limits

[neeraj-pilot]

Summary

• add signed browser admission tokens for public collection and file-link device limits
• apply collection admission to /public-collection/info and /public-collection/diff, and file-link admission to /file-link/info
• persist and send tokens from albums, embed, and share clients using header-only transport with Museum CORS support

Validation

• go test ./pkg/controller/public ./pkg/middleware ./pkg/api
• git diff --check
• Web typecheck not run: web/node_modules is missing, so workspace tsc commands fail with tsc not found

[chatgpt-codex-connector]

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Reviewed commit: 14ba926426

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[anandbaburajan]

Tested