refactor: replace Spacer with custom spacers

[ovitrif]

Description

This PR:

1. Adds a modifier parameter to all custom spacer components in Spacers.kt — VerticalSpacer, HorizontalSpacer, FillHeight, FillWidth, StatusBarSpacer, TopBarSpacer
2. Replaces all raw Spacer(modifier = Modifier.height/width/weight(...)) calls across 110 files with the appropriate semantic component

Each raw call was replaced according to context:

• Modifier.height(X) → VerticalSpacer(X)
• Modifier.width(X) → HorizontalSpacer(X)
• Modifier.weight(1f) in Column → FillHeight()
• Modifier.weight(1f) in Row → FillWidth()

Unused androidx.compose.foundation.layout.Spacer, height, and width imports were removed from each modified file. The FillHeight/FillWidth scope constraints (ColumnScope/RowScope) provide compile-time safety — any misidentified context would have caused a build failure.

Preview

N/A — pure refactor, no visual changes.

QA Notes

This is a structural refactor with no behaviour changes. Each custom spacer delegates to the same underlying Spacer with the same modifier. The Kotlin compiler enforces correct scope usage for FillHeight/FillWidth. Manual spot-check recommended on the highest-impact screens:

1. ExternalConnectionScreen
2. SendConfirmScreen
3. ActivityDetailScreen
4. HomeScreen
5. ReceiveQrScreen
6. ReportIssueScreen
7. SweepSettingsScreen
8. SavingsProgressScreen
9. LiquidityScreen
10. PinBiometricsScreen

For each screen: verify layout, spacing, and alignment look unchanged compared to master.

Automated checks

• ./gradlew compileDevDebugKotlin — passes
• ./gradlew detekt — passes (import ordering auto-corrected)
• ./gradlew testDevDebugUnitTest — 566 pass, 3 pre-existing CurrencyTest failures (locale-sensitive, unrelated to this PR, pass on CI)