Release v0.2.0 - Security and integrity features

- Add REST API response signing using HMAC-SHA256
- Add SHA256 hash validation for version file uploads
- Add ResponseSigner class for automatic API response signing
- Add file_hash column to database schema
- Remove external URL support from version uploads
- Update translations with all fuzzy strings resolved

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -36,6 +36,8 @@ This project is proudly **"vibe-coded"** using Claude.AI - the entire codebase w
 
 No known bugs at the moment
 
+No planned features at this time. See Session History for completed work.
+
 ## Technical Stack
 
 - **Language:** PHP 8.3.x
@@ -667,3 +669,51 @@ Security practices verified:
 - Created release package: `releases/wc-licensed-product-0.1.0.zip` (478 KB)
 - SHA256: `62638e240315107098be4cb40faff8395e9e1b719d79b73d80e69d680b305e87`
 - Tagged as `v0.1.0` and pushed to `main` branch
+
+### 2026-01-22 - Version 0.2.0 - Security & Integrity Features
+
+**Overview:**
+
+Added response signing for REST API security and SHA256 checksum validation for uploaded version files.
+
+**Implemented:**
+
+- REST API response signing using HMAC-SHA256 for tamper-proof responses
+- SHA256 hash field for product version uploads with server-side validation
+- Per-license key derivation using HKDF-like approach
+- Automatic signature headers on license API endpoints
+
+**Removed:**
+
+- External download URL field from product version form
+- Direct URL support in version uploads (Media Library only now)
+
+**New files:**
+
+- `src/Api/ResponseSigner.php` - HMAC-SHA256 response signing class
+
+**Modified files:**
+
+- `src/Installer.php` - Added `file_hash` column to versions table schema
+- `src/Product/ProductVersion.php` - Added `fileHash` property and getter
+- `src/Product/VersionManager.php` - Removed `$downloadUrl` parameter, added `$fileHash` with validation
+- `src/Admin/VersionAdminController.php` - Removed URL field, added SHA256 hash field
+- `assets/js/versions.js` - Updated form handling for hash field
+- `src/Plugin.php` - Initialize ResponseSigner when server secret is configured
+
+**Technical notes:**
+
+- Response signing only activates when `WC_LICENSE_SERVER_SECRET` constant is defined
+- Signature algorithm: `HMAC-SHA256(derived_key, timestamp + ':' + canonical_json)`
+- Key derivation: `HMAC-SHA256(HMAC-SHA256(license_key, server_secret) + "\x01", server_secret)`
+- Hash validation throws `InvalidArgumentException` on mismatch
+- Compatible with `magdev/wc-licensed-product-client` SecureLicenseClient
+- Database migration handled by WordPress `dbDelta()` function
+
+**Configuration:**
+
+To enable response signing, add to `wp-config.php`:
+
+```php
+define('WC_LICENSE_SERVER_SECRET', 'your-secure-random-string-min-32-chars');
+```