feat: connection issues view

[jvsena42]

Description

This PR adds a reusable connection issues overlay view that appears when the device loses internet connectivity during payment and transfer flows. The overlay shows a phone illustration with dashed gradient rings and a loading spinner, and auto-dismisses when connectivity is restored while preserving the underlying flow state.

Integrates the overlay into:

• Send Bitcoin sheet
• Receive Bitcoin sheet
• Force Transfer sheet
• Transfer to Spending screens (amount + confirm)
• Transfer to Savings confirm screen

Linked Issues/Tasks

• Android counterpart: feat: connection issues view bitkit-android#878
• Related to Port missing v60 UI/UX improvements to iOS #516

Screenshot / Video

QA Notes

OBS: If you are testing on emulator, you have to turn off the computer internet to simulate connection loss

1. Connection Issues Overlay - Send Sheet

1. Open the Send Bitcoin sheet
2. Toggle airplane mode on
3. Connection Issues overlay should fade in over the send flow
4. Title should read "Send Bitcoin"
5. Dashed yellow rings and phone illustration should be visible
6. Spinner should be animating at the bottom
7. Re-enable connectivity
8. Overlay should fade out and send flow state should be preserved

send-sheet.mp4

scan-sheet-zero-amount.mp4

2. Connection Issues Overlay - Receive Sheet

1. Open the Receive Bitcoin sheet
2. Toggle airplane mode on → overlay should appear with title "Receive Bitcoin"
3. Re-enable connectivity → overlay fades out, receive flow preserved

receive-screen.mp4

3. Connection Issues Overlay - Force Transfer

1. Open the Force Transfer sheet
2. Toggle airplane mode → overlay should appear with title "Transfer Funds"
3. Re-enable → overlay fades out

4. Connection Issues Overlay - Transfer to Spending

1. Navigate to Transfer to Spending amount screen
2. Toggle airplane mode → overlay appears
3. Re-enable → overlay fades out, amount preserved
4. Repeat on the confirm screen

transfer-to-spendings.mp4

5. Connection Issues Overlay - Transfer to Savings

1. Navigate to Transfer to Savings confirm screen
2. Toggle airplane mode → overlay appears
3. Re-enable → overlay fades out

transfer-to-savings.mp4

6. No False Positives

1. Navigate through all above flows with stable connectivity
2. The overlay should never appear

[jvsena42]

it looks like the other__connection_issue_explain toast is not implemented. I'll do it in other PR to keep this one as simple as possible

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.