Restructure repo layout, wiring src/ and packaging for local and distro builds

- Add dev runner main.py that prefers local src/ over installed pkgmgr
- Move Arch/Debian/Fedora packaging files under packaging/* and update build scripts
- Adjust .gitignore/.dockerignore for new packaging paths and src/source/
- Improve config defaults discovery to support src/ layout and installed packages
- Update architecture diagram and add TODO overview for TAGS/MIRROR/SIGNING_KEY

https://chatgpt.com/share/693a76a0-e408-800f-9939-868524cbef4d

.gitignore

@@ -15,16 +15,9 @@ dist/
 build/*
 *.egg-info/
 pkg
-src/source
+src/source/
 package-manager-*
 
-# debian 
-debian/package-manager/
-debian/debhelper-build-stamp
-debian/files
-debian/.debhelper/
-debian/package-manager.substvars
-
 # Editor files
 .vscode/
 .idea/