Widen macOS amount fields so large values don't clip

NumericField's macOS-only frame was hard-capped at 140pt, but the
app's own max BTC supply (21,000,000) means Sats amounts can reach a
~21-character grouped string, which didn't fit — the field visibly
clipped once typed input exceeded the cap. Lets it grow up to 220pt
instead of a fixed 140pt.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy

iosApp/iosApp/ContentView.swift

@@ -351,7 +351,12 @@ private struct NumericField: View {
             #endif
             .multilineTextAlignment(alignment)
             #if os(macOS)
-            .frame(maxWidth: 140)
+            // Bounded rather than unconstrained so the field doesn't grow to fill the whole row
+            // (the original reason for a fixed width here), but wide enough for the largest
+            // values this app actually displays — e.g. a Sats amount at the max BTC supply
+            // (`maxSupplyBtcAmount` * 100,000,000) is a 16-digit, comma-grouped ~21-character
+            // string, which a 140pt cap was clipping.
+            .frame(minWidth: 80, idealWidth: 140, maxWidth: 220)
             #endif
             .onAppear { text = NumberFormatKt.groupDigits(value: value) }
             .onChange(of: text) { newValue in