Release v4.1.5: Clean up docs, update release notes

- Remove old PLAN-4.1.x.md and RELEASE-4.1.1.md files
- Update RELEASE_NOTES.md for v4.1.5
- Highlights: dev docs, pull-image.sh auto-resize, 16GB images

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

RELEASE_NOTES.md

@@ -1,14 +1,41 @@
-## Stegasoo v4.1.3
+## Stegasoo v4.1.5
 
-### Fixes
-- **SSL Certificate Generation**: First-boot wizard now properly generates self-signed certs when HTTPS is enabled
-- **Download Bug Fixed**: No more "File expired or not found" errors - fixed multi-worker temp file sharing
-- **Docker Build**: Reduced build context from 2.3GB to ~900KB
+### Developer Experience
+- **Educational Code Comments**: Core modules now include detailed explanations
+  - DCT: zig-zag coefficient diagrams, QIM embedding math, Reed-Solomon "Voyager" reference
+  - LSB: visual bit manipulation examples, ChaCha20 pixel selection
+  - Crypto: multi-factor KDF flow diagrams, Argon2id memory-hardness reasoning
+  - CLI/Web: architectural patterns for future contributors
 
-### Improvements
-- Docker memory limits increased to 2GB (prevents OOM on large DCT operations)
-- Decode button now shows loading spinner during processing
-- Headless Pi flash script with Trixie/NetworkManager support
+### Raspberry Pi Improvements
+- **Streamlined Image Creation**: `pull-image.sh` now handles everything
+  - Auto-resizes rootfs to exactly 16GB (consistent images from any SD card)
+  - Disables Pi OS auto-expand
+  - Compresses with zstd
+  - Optional .zst.zip wrapper for GitHub releases
+- **16GB Minimum**: Pre-built images are now 16GB (was variable)
+- **Host Requirements**: `rpi/host-requirements.txt` documents all dependencies
+- **Test Automation**: `kickoff-pi-test.sh` for one-command flash+test cycles
+
+### MOTD Polish
+- Dynamic temperature emoji (ice/cool/fire based on CPU temp)
+- Rocket emoji for service status
+- Cleaner formatting
+
+### Raspberry Pi Image
+Download `stegasoo-rpi-4.1.5.img.zst.zip` from Releases.
+
+```bash
+# Flash (auto-detects SD card)
+sudo ./rpi/flash-image.sh stegasoo-rpi-4.1.5.img.zst.zip
+
+# Or manual
+zstdcat stegasoo-rpi-4.1.5.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
@@ -16,19 +43,5 @@ docker-compose up -d web  # Web UI on :5000
 docker-compose up -d api  # REST API on :8000
 ```
 
-### Raspberry Pi Image
-Download `stegasoo-rpi-4.1.3.img.zst`, flash to SD card, and boot. The first-boot wizard will guide you through WiFi, HTTPS, and channel key setup.
-
-```bash
-# Flash with included script
-./rpi/flash-image.sh stegasoo-rpi-4.1.3.img.zst /dev/sdX
-
-# First time: save your WiFi credentials
-./rpi/inject-wifi.sh --setup
-
-# Then inject WiFi after flashing
-sudo ./rpi/inject-wifi.sh /dev/sdX
-```
-
 ### Full Changelog
-See [CHANGELOG.md](CHANGELOG.md) for complete details.
+See [CHANGELOG.md](CHANGELOG.md) for complete version history.