Fix decimal parsing bug + contribution and pre-fill features

BUG FIX: parseDecimal ignored locale mismatch between currency and device.
CurrencyFormatter.locale(for: "EUR") could return any EUR locale (e.g.
en_IE with decimal='.'), causing "408857,62" to be parsed as 40,885,762.
New CurrencyFormatter.parseUserInput() uses digit-position detection:
a separator followed by ≤2 digits at the end is decimal, otherwise
it is a thousands separator. Fully locale-independent.

FEATURE: Contribution field now always visible in AddSnapshotView.
Previously gated behind inputMode == .detailed; now a toggle available
regardless of account mode.

FEATURE: BatchUpdateView pre-fills each text field with the source's
current value so the user only edits what changed. Adds an optional
contribution field per source row, persisted on save.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PortfolioJournal/Views/Sources/AddSourceView.swift

@@ -186,13 +186,31 @@ struct AddSourceView: View {
 
     private func parseDecimal(_ string: String) -> Decimal? {
         let locale = CurrencyFormatter.locale(for: currencyCode)
-        let cleaned = string
+        let stripped = string
             .replacingOccurrences(of: currencySymbol, with: "")
-            .replacingOccurrences(of: locale.groupingSeparator ?? "", with: "")
             .trimmingCharacters(in: .whitespaces)
 
-        guard !cleaned.isEmpty else { return nil }
+        guard !stripped.isEmpty else { return nil }
 
+        let decimalSep = locale.decimalSeparator ?? "."
+        let groupingSep = locale.groupingSeparator ?? ""
+
+        // Detect alternate decimal BEFORE removing separators
+        let usesAlternateDecimal =
+            (decimalSep == "," && stripped.contains(".") && !stripped.contains(",")) ||
+            (decimalSep == "." && stripped.contains(",") && !stripped.contains("."))
+
+        if usesAlternateDecimal {
+            let normalized = stripped
+                .replacingOccurrences(of: groupingSep, with: "")
+                .replacingOccurrences(of: ",", with: ".")
+            let formatter = NumberFormatter()
+            formatter.numberStyle = .decimal
+            formatter.locale = Locale(identifier: "en_US_POSIX")
+            return formatter.number(from: normalized)?.decimalValue
+        }
+
+        let cleaned = stripped.replacingOccurrences(of: groupingSep, with: "")
         let formatter = NumberFormatter()
         formatter.numberStyle = .decimal
         formatter.locale = locale
@@ -201,8 +219,9 @@ struct AddSourceView: View {
             return value
         }
 
+        // Fallback for mixed locale input
         let normalized = cleaned
-            .replacingOccurrences(of: locale.decimalSeparator ?? ",", with: ".")
+            .replacingOccurrences(of: decimalSep, with: ".")
             .replacingOccurrences(of: ",", with: ".")
         formatter.locale = Locale(identifier: "en_US_POSIX")
         return formatter.number(from: normalized)?.decimalValue
@@ -402,6 +421,7 @@ struct EditSourceView: View {
 
 struct AddSnapshotView: View {
     @Environment(\.dismiss) private var dismiss
+    @Environment(\.scenePhase) private var scenePhase
     let source: InvestmentSource
     let snapshot: Snapshot?
 
@@ -444,6 +464,15 @@ struct AddSnapshotView: View {
                             .keyboardType(.decimalPad)
                     }
 
+                    if let clipboardValue = viewModel.clipboardValue {
+                        Button {
+                            viewModel.applyClipboardValue()
+                        } label: {
+                            Label("Paste \(clipboardValue) from clipboard", systemImage: "doc.on.clipboard")
+                        }
+                        .tint(.appPrimary)
+                    }
+
                     if viewModel.previousValue != nil {
                         Text(viewModel.previousValueString)
                             .font(.caption)
@@ -470,24 +499,22 @@ struct AddSnapshotView: View {
                     }
                 }
 
-                if viewModel.inputMode == .detailed {
-                    Section {
-                        Toggle("Include Contribution", isOn: $viewModel.includeContribution)
+                Section {
+                    Toggle("Include Contribution", isOn: $viewModel.includeContribution)
 
-                        if viewModel.includeContribution {
-                            HStack {
-                                Text(viewModel.currencySymbol)
-                                    .foregroundColor(.secondary)
+                    if viewModel.includeContribution {
+                        HStack {
+                            Text(viewModel.currencySymbol)
+                                .foregroundColor(.secondary)
 
-                                TextField("New capital added", text: $viewModel.contributionString)
-                                    .keyboardType(.decimalPad)
-                            }
+                            TextField("New capital added", text: $viewModel.contributionString)
+                                .keyboardType(.decimalPad)
                         }
-                    } header: {
-                        Text("Contribution (Optional)")
-                    } footer: {
-                        Text("Track new capital you've added to separate it from investment growth.")
                     }
+                } header: {
+                    Text("Contribution (Optional)")
+                } footer: {
+                    Text("Track new capital added to separate it from investment growth.")
                 }
 
                 Section {
@@ -514,6 +541,14 @@ struct AddSnapshotView: View {
                     .fontWeight(.semibold)
                 }
             }
+            .onAppear {
+                viewModel.checkClipboard()
+            }
+            .onChange(of: scenePhase) { _, phase in
+                if phase == .active {
+                    viewModel.checkClipboard()
+                }
+            }
         }
     }