Update docs and comments for jpeglib migration (v4.2.0)

- Replace jpegio references with jpeglib in comments/docstrings
- Update sanitize-for-image.sh to use system Python 3.11+ (no pyenv)
- Update rpi/patches/README.md for jpeglib world
- Add AUR build artifacts to .gitignore

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

rpi/patches/README.md

@@ -2,56 +2,39 @@
 
 This directory contains patches for dependencies that need modifications to build on ARM64.
 
+## Current Status (v4.2+)
+
+As of Stegasoo 4.2, we use **jpeglib** instead of jpegio. The jpeglib build process is handled inline in `setup.sh` and includes:
+
+- Cloning from GitHub (PyPI tarball missing headers)
+- Downloading libjpeg headers for each version (6b through 9f)
+- Patching setup.py to skip turbo/mozjpeg (need cmake-generated headers)
+
+See `setup.sh` for the full implementation.
+
+## Legacy: jpegio Patches (v4.1 and earlier)
+
+The `jpegio/` directory contains patches for the old jpegio dependency, which required removing x86-specific `-m64` compiler flags. These are no longer used but kept for reference.
+
+## jpeglib Helper Script
+
+The `jpeglib/install-jpeglib-arm64.sh` script is a standalone version of the jpeglib build process. It's not used by setup.sh (which has the logic inline) but can be useful for manual testing or debugging.
+
 ## Structure
 
 ```
 patches/
-  <package>/
-    arm64.patch       # Standard unified diff patch file
-    apply-patch.sh    # Script with fallback strategies
+  jpegio/           # Legacy (v4.1) - not used in v4.2+
+    arm64.patch
+    apply-patch.sh
+  jpeglib/          # Reference script for manual builds
+    install-jpeglib-arm64.sh
 ```
 
-## How It Works
+## Adding New Patches
 
-The `apply-patch.sh` script tries multiple strategies in order:
-
-1. **Patch file** - Apply the `.patch` file using `patch -p1`
-2. **Sed fallback** - Use sed for simple string replacements
-3. **Python fallback** - Use regex for flexible pattern matching
-
-This layered approach handles:
-- Exact matches (patch file works)
-- Minor upstream changes (sed catches variations)
-- Significant changes (Python regex is most flexible)
-- Already patched files (detected and skipped)
-
-## Adding a New Patch
+If a new dependency needs ARM64 patches:
 
 1. Create a directory: `patches/<package>/`
-2. Create the patch file: `git diff > arm64.patch`
-3. Create `apply-patch.sh` with appropriate fallback logic
-4. Update `setup.sh` to call the patch script
-
-## jpegio Patch
-
-The jpegio library includes x86-specific `-m64` compiler flags that fail on ARM64.
-The patch removes these flags by replacing:
-
-```python
-cargs.append('-m64')
-```
-
-with:
-
-```python
-pass  # ARM64: removed x86-specific -m64 flag
-```
-
-## Updating Patches
-
-When upstream changes break a patch:
-
-1. Clone the new version
-2. Make the necessary modifications
-3. Generate a new patch: `diff -u original modified > arm64.patch`
-4. Test on a fresh Pi install
+2. Add patch files or helper scripts
+3. Update `setup.sh` to apply the patch during installation