docs: Update CHANGELOG and test mocks for Contract v1 migration

- Add Contract v1 breaking changes to CHANGELOG.md
- Document field name changes (fetchedAt→fetchTime, url→mediaUrl)
- Update test mocks in www/index.html and ios/App/App/public/index.html
- Mocks now return Contract v1 format (fetchTime, title, body, ttlSeconds)

BREAKING CHANGE: API responses now use Contract v1 field names.
See docs/CONTRACT_V1_BREAKING_CHANGES.md for migration guide.

CHANGELOG.md

@@ -5,6 +5,39 @@ All notable changes to the Daily Notification Plugin will be documented in this
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Breaking Changes
+
+- **Contract v1 Migration**: API responses now use Contract v1 field names
+  - `fetchedAt` → `fetchTime` (epoch ms) - All content cache API methods now return `fetchTime` instead of `fetchedAt`
+  - `url` → `mediaUrl` - Media URL field renamed to match Contract v1
+  - `payload` (string) → structured fields - Response now includes `title`, `body`, and `metadata` instead of raw `payload` string
+  - `meta` field removed - Replaced by structured `metadata` object
+  - **Affected Methods**: `getContentCache()`, `getContentCacheById()`, `getLatestContentCache()`, `getContentCacheHistory()`
+  - **Migration Guide**: See `docs/CONTRACT_V1_BREAKING_CHANGES.md` for details
+  - **TypeScript Interface**: `ContentCache` interface updated to match Contract v1 (legacy fields marked as deprecated)
+
+### Added
+
+- **Contract v1 Freeze**: Contract v1 directive and validation system
+  - Contract v1 defined and frozen (`contracts/NotificationContract.v1.ts`)
+  - Contract validation script (`./scripts/check-contract.sh`)
+  - Pre-commit hook for contract validation (optional)
+  - DTOs and mappers for iOS and Android to ensure Contract v1 compliance
+  - See `docs/0017-Daily-Notification-Contract-Freeze.md` for details
+
+- **Cross-Platform DTOs**: Data Transfer Objects for Contract v1
+  - iOS: `NotificationContentDTO` and `NotificationContentMapper`
+  - Android: `NotificationContentDTO` and `NotificationContentMapper`
+  - Ensures consistent field names and types across platforms
+
+### Changed
+
+- **API Response Format**: All content cache methods now return Contract v1 format
+  - Structured response with `title`, `body`, `fetchTime`, `mediaUrl`, `ttlSeconds`, etc.
+  - Legacy fields (`fetchedAt`, `payload`, `meta`) deprecated but may be present for backward compatibility
+
 ## [2.1.0] - 2025-01-02
 
 ### Added

ios/App/App/public/index.html

@@ -325,8 +325,11 @@
                 },
                 getContentCache: async () => {
                     return Promise.resolve({
-                        'cache-key-1': { content: 'Mock cached content', timestamp: Date.now() },
-                        'cache-key-2': { content: 'Another mock item', timestamp: Date.now() - 3600000 }
+                        id: 'mock-cache-001',
+                        title: 'Mock Notification',
+                        body: 'Mock cached content',
+                        fetchTime: Date.now(), // Contract v1 (epoch ms)
+                        ttlSeconds: 3600
                     });
                 },
                 clearContentCache: async () => {

www/index.html

@@ -325,8 +325,11 @@
                 },
                 getContentCache: async () => {
                     return Promise.resolve({
-                        'cache-key-1': { content: 'Mock cached content', timestamp: Date.now() },
-                        'cache-key-2': { content: 'Another mock item', timestamp: Date.now() - 3600000 }
+                        id: 'mock-cache-001',
+                        title: 'Mock Notification',
+                        body: 'Mock cached content',
+                        fetchTime: Date.now(), // Contract v1 (epoch ms)
+                        ttlSeconds: 3600
                     });
                 },
                 clearContentCache: async () => {