feat(i18n): complete internationalization for iOS + watchOS across all views

Migrate every hardcoded Text("...") string to the L10n / LocalizedStringResource
type-safe key system with full en/fr/de/es translations (4 languages).

iOS changes (TabataGo target):
- Strings.swift: ~90 new L10n keys across 13 groups (action, tab, home, zone,
  level, programs, programDetail, player, profile, settings, policy, paywall,
  health, complete, activity, onboarding, goal)
- Localizable.xcstrings: 145 → 245+ keys with fr/de/es translations
- Model enums: FitnessLevel.label & FitnessGoal.label changed from String to
  LocalizedStringResource, backed by L10n.level/goal keys
- Component param types changed to LocalizedStringResource: StatBadge,
  SectionHeader, ProfileRow, PolicySection, CompletionStat, FeatureRow,
  OnboardingHeader, PrimaryButton, SelectionCard
- All 18 view files updated: HomeTab, ActivityTab, ProgramsTab, ProfileTab,
  MainTabView, SettingsView, PolicyViews, CompletionView, BodyZoneView,
  ProgramDetailView, PaywallView, OnboardingView, PlayerView

Watch changes (TabataGoWatch target):
- New Localizable.xcstrings: 23 keys with en/fr/de/es (phase labels, idle
  state, activity rings, complication strings)
- New WatchL10n.swift: type-safe enum (needs manual Xcode target membership)
- Updated: WatchPlayerView, WatchIdleView, WatchActivityView,
  TabataGoComplication (inline LocalizedStringResource for widget target)

Both iOS and watchOS targets build with zero errors.

tabatago-swift/TabataGoWatch/Utilities/WatchL10n.swift

@@ -0,0 +1,54 @@
+import Foundation
+
+/// Type-safe string keys for the Watch target's `Localizable.xcstrings`.
+/// Usage: Text(WatchL10n.phase.work)  or  String(localized: WatchL10n.idle.connected)
+enum WatchL10n {
+
+    enum phase {
+        static let getReady  = LocalizedStringResource("watch.phase.getReady")
+        static let warmUp    = LocalizedStringResource("watch.phase.warmUp")
+        static let work      = LocalizedStringResource("watch.phase.work")
+        static let rest      = LocalizedStringResource("watch.phase.rest")
+        static let `break`   = LocalizedStringResource("watch.phase.break")
+        static let coolDown  = LocalizedStringResource("watch.phase.coolDown")
+        static let done      = LocalizedStringResource("watch.phase.done")
+
+        static func label(for phase: WatchPhase) -> LocalizedStringResource {
+            switch phase {
+            case .prep:           return getReady
+            case .warmup:         return warmUp
+            case .work:           return work
+            case .rest:           return rest
+            case .interBlockRest: return `break`
+            case .cooldown:       return coolDown
+            case .complete:       return done
+            }
+        }
+    }
+
+    enum idle {
+        static let startOnPhone = LocalizedStringResource("watch.idle.startOnPhone")
+        static let connected    = LocalizedStringResource("watch.idle.connected")
+        static let noPhone      = LocalizedStringResource("watch.idle.noPhone")
+    }
+
+    enum activity {
+        static let today    = LocalizedStringResource("watch.activity.today")
+        static let move     = LocalizedStringResource("watch.activity.move")
+        static let exercise = LocalizedStringResource("watch.activity.exercise")
+        static let stand    = LocalizedStringResource("watch.activity.stand")
+        static let streak   = LocalizedStringResource("watch.activity.streak")
+    }
+
+    enum complication {
+        static let notStarted    = LocalizedStringResource("watch.complication.notStarted")
+        static let today         = LocalizedStringResource("watch.complication.today")
+        static let yesterday     = LocalizedStringResource("watch.complication.yesterday")
+        /// printf format: takes one Int (number of days). e.g. "%d days ago"
+        static let daysAgoFmt    = LocalizedStringResource("watch.complication.daysAgoFmt")
+        /// printf format: takes one Int (streak count). e.g. "%d day streak"
+        static let dayStreakFmt  = LocalizedStringResource("watch.complication.dayStreakFmt")
+        static let openApp       = LocalizedStringResource("watch.complication.openApp")
+        static let description   = LocalizedStringResource("watch.complication.description")
+    }
+}