Finalize 4.1.4 release prep

- BUILD_IMAGE.md: Clarify docs are for devs, not end users
- Add 4.1.5 plan with decode progress bar feature
- Update .gitignore for release assets (.zip, .img)

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

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

rpi/BUILD_IMAGE.md

@@ -1,5 +1,8 @@
 # Stegasoo Pi Image Build Workflow
 
+> **Note:** This guide is for developers building custom Pi images.
+> **End users:** Just download the pre-built `.img.zst` from [Releases](https://github.com/adlee-was-taken/stegasoo/releases), flash it, and boot. No build process needed.
+
 Quick reference for building a distributable SD card image.
 
 ## Step 1: Flash Fresh Raspbian
@@ -39,6 +42,9 @@ git clone -b 4.1 https://github.com/adlee-was-taken/stegasoo.git stegasoo
 
 ## Step 5: Copy Pre-built Tarball (from host)
 
+> **Dev-only asset:** This tarball is for building Pi images, not for end users.
+> It's available on [Releases](https://github.com/adlee-was-taken/stegasoo/releases) for image builders.
+
 ```bash
 # On your host machine:
 scp rpi/stegasoo-pi-arm64.tar.zst admin@stegasoo.local:/opt/stegasoo/rpi/