feat: add print stylesheet section for ReceiptShare (Closes #765)

[waterWang]

Summary

Add print stylesheet section for ReceiptShare [b#031] (GrantFox FWC26).

Changes

• src/pages/ReceiptShare.tsx: Added .receiptshare-page and .receiptshare-chrome class names for print targeting
• src/styles/print.css: Added @media print block for ReceiptShare that hides chrome, resets colors to light mode, and prevents page breaks inside receipt cards
• src/pages/tests/ReceiptShare.print.test.tsx: Focused tests verifying that the print stylesheet contains the expected selectors and the component applies the correct class names

Verification

• All existing tests continue to pass
• The new @media print block follows the same pattern as the existing ClaimFlow and DisputeCard print blocks in src/styles/print.css

Closes #765

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