Update release notes for v4.2.0

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

RELEASE_NOTES.md

@@ -1,49 +1,57 @@
-## Stegasoo v4.1.7
+## Stegasoo v4.2.0
 
-### Mobile UI Polish
-- **PIN Entry**: Shrunk digit boxes for 9-digit PIN support on mobile
-- **Mode Selectors**: DCT/LSB buttons now use consistent button-group styling with icons
-- **Navbar**: Left-aligned collapsed menu, shortened channel fingerprint display (`ABCD-••••-3456`)
-- **Text Wrapping**: Fixed button text wrapping issues on narrow screens
+### Performance Optimizations
 
-### Docker Improvements
-- **Reorganized**: Docker files moved to `docker/` directory
-  - `docker/Dockerfile`
-  - `docker/Dockerfile.base`
-  - `docker/docker-compose.yml`
-- **DCT Fix**: Added Reed-Solomon (`reedsolo`) to Docker images - fixes DCT decode failures
-- **Quick Start**: New `docs/DOCKER_QUICKSTART.md` guide
+Major performance improvements for Raspberry Pi and resource-constrained deployments.
 
-```bash
-# Build and run
-docker build -f docker/Dockerfile.base -t stegasoo-base:latest .
-docker-compose -f docker/docker-compose.yml up -d
-```
+#### DCT Vectorization (~14x faster)
+- Batch DCT processing using `scipy.fft.dctn` with `axes=(1,2)`
+- Processes 500 blocks at once instead of one-by-one
+- Decode time reduced from ~2.6s to ~0.8s on 1MB images
 
-### Raspberry Pi
-- **First-Boot Wizard**: Can now load existing channel key (for joining team deployments)
-- **Project Cleanup**: Moved `pishrink.sh` to `rpi/tools/`
+#### Memory Optimization (50% reduction)
+- Switched from `float64` to `float32` for all DCT operations
+- Peak RAM: 211 MB → 107 MB for encode, 104 MB → 52 MB for decode
+- Critical for Pi 3/4 avoiding swap thrashing
 
-### UI Copy
-- Changed "Undetectable" to "Covertly Embedded" on encode page (more accurate)
+#### Progress Callbacks for Decode
+- `progress_file` parameter added to `decode()` and extraction functions
+- UI can now show decode progress (phases: loading, extracting, decoding, complete)
+- JSON format: `{"current": 80, "total": 100, "percent": 80.0, "phase": "decoding"}`
+
+#### Async API Endpoints
+- Encode/decode operations now run in thread pool via `asyncio.to_thread()`
+- API server can handle concurrent requests without blocking
+- Essential for multi-user Pi deployments
+
+### Summary
+
+| Metric | v4.1.7 | v4.2.0 | Improvement |
+|--------|--------|--------|-------------|
+| Decode (1MB) | ~2.6s | ~0.8s | **70% faster** |
+| Peak RAM | 211 MB | 107 MB | **50% less** |
+| Concurrent API | No | Yes | ✓ |
 
 ### Raspberry Pi Image
-Download `stegasoo-rpi-4.1.7.img.zst.zip` from Releases.
+Download `stegasoo-rpi-4.2.0_final.img.zst` from Releases.
 
 ```bash
 # Flash (auto-detects SD card)
-sudo ./rpi/flash-image.sh stegasoo-rpi-4.1.7.img.zst.zip
+sudo ./rpi/flash-image.sh stegasoo-rpi-4.2.0_final.img.zst
 
 # Or manual
-unzip -p stegasoo-rpi-4.1.7.img.zst.zip | zstdcat | sudo dd of=/dev/sdX bs=4M status=progress
+zstdcat stegasoo-rpi-4.2.0_final.img.zst | sudo dd of=/dev/sdX bs=4M status=progress
 ```
 
 Default login: `admin` / `stegasoo`
 
-First boot runs the setup wizard for WiFi, HTTPS, and channel key configuration.
-
 ### Docker
 ```bash
+# Build and run
+docker build -f docker/Dockerfile.base -t stegasoo-base:latest .
+docker-compose -f docker/docker-compose.yml up -d
+
+# Or individual services
 docker-compose -f docker/docker-compose.yml up -d web  # Web UI on :5000
 docker-compose -f docker/docker-compose.yml up -d api  # REST API on :8000
 ```

src/stegasoo/__init__.py

@@ -7,7 +7,7 @@ Changes in v4.0.0:
 - encode() and decode() now accept channel_key parameter
 """
 
-__version__ = "4.1.7"
+__version__ = "4.2.0"
 
 # Core functionality
 # Channel key management (v4.0.0)