feat(mobile): hide credit balance with a toggle

[iscekic]

Summary

• Remove screenshot blocking on the profile tab (Recents cover, Android FLAG_SECURE, and the modal close-on-cover wiring).
• Add a muted eye button in line with the credit balance. Tap hides the amount as ***** and hides the expiring-credits line so it cannot leak the number.
• The choice persists in SecureStore across app reboots. Default is visible.

Verification

• Mounted credits-card test: hide then show toggles $10.00 and *****.
• Mobile unit suite: 9255 tests passed.
• No device run in this session. Confirm on a build: Profile → tap the eye → leave the app → relaunch → balance still masked.

Visual Changes

N/A — no device screenshots in this session.

Before	After
Profile Recents card is blank. Balance always visible in-app.	Recents shows the screen. Balance has a small eye control; hidden state is *****.

Reviewer Notes

• Preference is device-level (same store as theme). It is not cleared on sign-out, so a shared device keeps the last hide choice.
• expo-screen-capture is removed. A native rebuild is required for that uninstall to land in the binary.
• Hidden state waits for the SecureStore read so a cached balance cannot flash before *****.