Bump version to 4.1.3

- Version bump from 4.1.2 to 4.1.3
- Updated CHANGELOG with SSL cert fix as highlight
- Added *.img.zst.zip to .gitignore

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

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

src/stegasoo/__init__.py

@@ -7,7 +7,7 @@ Changes in v4.0.0:
 - encode() and decode() now accept channel_key parameter
 """
 
-__version__ = "4.1.2"
+__version__ = "4.1.3"
 
 # Core functionality
 # Channel key management (v4.0.0)

src/stegasoo/constants.py

@@ -25,7 +25,7 @@ from pathlib import Path
 # VERSION
 # ============================================================================
 
-__version__ = "4.1.2"
+__version__ = "4.1.3"
 
 # ============================================================================
 # FILE FORMAT