Fix iOS time display and add timer unit labels

Times were always showing 0 because ISO8601DateFormatter with default
options does not parse fractional seconds, but Prisma/Node.js serialises
dates as "2026-02-20T09:00:00.000Z" (with .000). Every date(from:) call
silently returned nil, so elapsedTime and duration always fell back to 0.

- Date+Extensions: fromISO8601 now tries .withFractionalSeconds first,
  then falls back to whole seconds — single place to maintain
- OngoingTimer.elapsedTime: use Date.fromISO8601() instead of bare formatter
- TimeEntry.duration: use Date.fromISO8601() instead of bare formatters
- TimerView: add TimerUnitLabels view showing h/min/sec column headers
  under the monospaced clock digits

ios/TimeTracker/TimeTracker/Features/Timer/TimerView.swift

@@ -44,6 +44,8 @@ struct TimerView: View {
                     .font(.system(size: 64, weight: .light, design: .monospaced))
                     .foregroundStyle(viewModel.activeTimer != nil ? .primary : .secondary)
                 
+                TimerUnitLabels(elapsed: viewModel.elapsedTime)
+                
                 if let project = viewModel.selectedProject {
                     ProjectColorBadge(
                         color: project.color,
@@ -123,7 +125,31 @@ struct TimerView: View {
     }
 }
 
-struct ProjectPickerSheet: View {
+/// Displays "h  min  sec" (or "min  sec") column labels aligned under the
+/// monospaced timer digits.
+private struct TimerUnitLabels: View {
+    let elapsed: TimeInterval
+
+    private var showHours: Bool { Int(elapsed) >= 3600 }
+
+    var body: some View {
+        HStack(spacing: 0) {
+            if showHours {
+                Text("h")
+                    .frame(width: 64)
+                Text("min")
+                    .frame(width: 64)
+            } else {
+                Text("min")
+                    .frame(width: 64)
+            }
+            Text("sec")
+                .frame(width: 64)
+        }
+        .font(.caption)
+        .foregroundStyle(.secondary)
+    }
+}
     let projects: [Project]
     let selectedProject: Project?
     let onSelect: (Project?) -> Void

ios/TimeTracker/TimeTracker/Models/OngoingTimer.swift

@@ -9,9 +9,7 @@ struct OngoingTimer: Codable, Identifiable, Equatable {
     let updatedAt: String
     
     var elapsedTime: TimeInterval {
-        guard let start = ISO8601DateFormatter().date(from: startTime) else {
-            return 0
-        }
+        guard let start = Date.fromISO8601(startTime) else { return 0 }
         return Date().timeIntervalSince(start)
     }
 }

ios/TimeTracker/TimeTracker/Models/TimeEntry.swift

@@ -11,10 +11,8 @@ struct TimeEntry: Codable, Identifiable, Equatable {
     let updatedAt: String
     
     var duration: TimeInterval {
-        guard let start = ISO8601DateFormatter().date(from: startTime),
-              let end = ISO8601DateFormatter().date(from: endTime) else {
-            return 0
-        }
+        guard let start = Date.fromISO8601(startTime),
+              let end = Date.fromISO8601(endTime) else { return 0 }
         return end.timeIntervalSince(start)
     }
 }

ios/TimeTracker/TimeTracker/Shared/Extensions/Date+Extensions.swift

@@ -59,8 +59,14 @@ extension Date {
     }
     
     static func fromISO8601(_ string: String) -> Date? {
-        let formatter = ISO8601DateFormatter()
-        formatter.formatOptions = [.withInternetDateTime]
-        return formatter.date(from: string)
+        // Try with fractional seconds first (e.g. "2026-02-20T09:00:00.000Z" from
+        // Prisma/Node.js JSON serialisation), then fall back to whole seconds.
+        let withFractional = ISO8601DateFormatter()
+        withFractional.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        if let date = withFractional.date(from: string) { return date }
+
+        let wholeSec = ISO8601DateFormatter()
+        wholeSec.formatOptions = [.withInternetDateTime]
+        return wholeSec.date(from: string)
     }
 }