Add a clear invalid/expired QR error screen with rescan action

[Lakes41]

Difficulty: Intermediate
Type: UI/UX

Background
The README states that invalid QR payloads (bad type/version, malformed JSON, missing fields, invalid wallet, expired) are rejected before the access check is submitted, implying a rejection UI already exists in some form on the access-scanner screen.

Problem
It's not clear the rejection UI distinguishes between different failure reasons (e.g., "this QR code has expired" vs. "this isn't a GuildPass QR code" vs. "malformed code") or offers an immediate one-tap rescan action — a generic "invalid QR code" message is less helpful for users trying to figure out what went wrong.

Expected outcome
When a scanned QR payload fails validation, the scanner shows a specific, human-readable reason (matching the validation case that failed) and a prominent "Scan Again" button that immediately resumes scanning without navigating away from the screen.

Suggested implementation

• Ensure the QR validation function (from src/features/access/) returns a discriminated result type identifying which specific check failed, not just a boolean.
• Map each failure reason to a specific, friendly message in app/access-scanner.tsx.
• Add a "Scan Again" button that resets scanner state without a full screen remount/navigation.
• Add a Maestro E2E step (or extend an existing one) verifying the rescan button correctly resumes camera scanning.

Acceptance criteria

• Each documented validation failure shows a distinct, specific message
• "Scan Again" resumes scanning immediately without leaving the screen
• Covered by at least one E2E test step

Likely affected files/directories

• app/access-scanner.tsx
• src/features/access/
• .maestro/

[EngrEOOnoja]

I'd like to take this on. I'll change the QR validator to return a discriminated result identifying the specific failure reason, map each case to a friendly message on the scanner screen, add a "Scan Again" button that resets scanner state without navigating away, and extend the Maestro E2E suite to cover the rescan flow.

[grantfox-oss]

🦊 GrantFox — @EngrEOOnoja has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #238)
2. Your PR will be reviewed by the Adamantine-guild maintainers

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