Workouts 2.0: re-base persistence on iCloud Drive documents

Replace Core Data + NSPersistentCloudKitContainer + App-Group store +
WatchConnectivity dictionary sync with the QuickRabbit iCloud-documents
architecture:

- iCloud Drive JSON documents are the sole source of truth (one file per
  aggregate: Splits/<ULID>.json, Workouts/YYYY/MM/<ULID>.json), with a
  rebuildable SwiftData cache populated only by an NSMetadataQuery observer
  and a connect-time reconcile. Soft-delete tombstones; hard iCloud gate.
- Shared model layer (ULID, Codable *Documents + stateless mappers, @Model
  cache entities, SwiftData container) compiled into both targets.
- New iPhone<->Watch bridge over WatchConnectivity keyed by ULIDs; the phone
  is the sole writer of iCloud Drive, the watch round-trips documents.
- AppServices DI + iCloud-required root gate; Swift 6 strict concurrency.
- Starter splits generated on demand from the bundled YAML catalogs.
- Migrate to XcodeGen (project.yml), iOS 26 / watchOS 26; CloudDocuments
  entitlement (drop CloudKit/App Group/aps-environment).
- Duration stored as Int seconds (was a Date epoch hack); fix workout
  end-on-create, undismissable delete dialog, toolbar-hiding nav stacks,
  and the Settings placeholder.
- Add README/CHANGELOG/LICENSE, .gitignore, refreshed REQUIREMENTS, and the
  Scripts/ TestFlight pipeline (release.sh + ASC API scripts).

MARKETING_VERSION 2.0.

.env.release.example

@@ -0,0 +1,11 @@
+# Copy to .env.release (gitignored) and fill in. Used by Scripts/release.sh.
+#
+# Apple Developer team that signs the build (same as DEVELOPMENT_TEAM).
+APPLE_TEAM_ID=
+
+# App Store Connect API key (App Store Connect > Users and Access > Integrations > App Store Connect API).
+# Create a key with "App Manager" access, download the .p8 ONCE, and store it somewhere safe.
+ASC_KEY_ID=
+ASC_ISSUER_ID=
+# Absolute path to the downloaded AuthKey_XXXXXXXXXX.p8 file.
+ASC_KEY_PATH=