Solves #752 (comment)

This PR lifts the hideBalance state from ActivityDetailContent to its parent ActivityDetailScreen, following the parent-child composable pattern.

Description

The ActivityDetailContent composable was accessing settingsViewModel directly instead of receiving state as a parameter from its parent. This violated the CLAUDE.md rule: "ALWAYS split screen composables into parent accepting viewmodel + inner private child accepting state and callbacks".

Changes:

1. Moves settingsViewModel and hideBalance state access to parent ActivityDetailScreen
2. Adds hideBalance: Boolean parameter to ActivityDetailContent
3. Passes state from parent to child

Preview

N/A - No visual changes, refactoring only

QA Notes

1. Hide balance on activity detail

1. Open the wallet
2. Swipe on the balance to hide it
3. Tap on any activity in the list
4. Verify the header balance shows • • • • • • • • •
5. Verify the payment amount shows • • • • •
6. Verify the fee amount shows • • • • • (if applicable)

2. Show balance on activity detail

1. Ensure balance is visible (not hidden)
2. Tap on any activity
3. Verify all amounts display correctly with proper currency formatting