docs(readme): migrate demo to YouTube and apply KISS principle

CHANGES
- Replace local video links with YouTube hosting for reliability
- Remove clickable thumbnail section for simplified presentation
- Add source recording and rename thumbnail for consistency
- Complete decoupling from external Loom dependency

IMPACT
- Consistent demo playback across all platforms and viewers
- Simplified documentation following KISS principle
- Eliminates GitHub video preview inconsistencies

TECHNICAL NOTES
- YouTube link: https://youtu.be/3nVp46Q8FdY
- Local assets retained for documentation purposes
- Thumbnail renamed to 2025-07-27-demo-thumbnail.png for consistency

Author: KemingHe

README-dockerhub.md

@@ -2,7 +2,7 @@
 
 > README updated on 2025-07-27 by [@KemingHe](https://github.com/KemingHe)
 
-Stop getting out-of-date Python package manager commands from your AI. Cross-reference latest official `pip`, `poetry`, `uv`, and `conda` docs with auto-updates. [[Watch Demo]](https://github.com/KemingHe/python-dependency-manager-companion-mcp-server/blob/main/docs/assets/2025-07-27-demo.mp4)
+Stop getting out-of-date Python package manager commands from your AI. Cross-reference latest official `pip`, `poetry`, `uv`, and `conda` docs with auto-updates. [[Watch Demo on YouTube]](https://youtu.be/3nVp46Q8FdY)
 
 ## 🚀 Quick Start for Agentic IDEs
 

README.md

@@ -2,11 +2,7 @@
 
 > README updated on 2025-07-27 by [@KemingHe](https://github.com/KemingHe)
 
-Stop getting out-of-date Python package manager commands from your AI. Cross-reference latest official `pip`, `poetry`, `uv`, and `conda` docs with auto-updates.
-
-**Click to play demo**:
-
-[![Watch Demo](./docs/assets/py-dep-man-companion-demo-thumbnail.png)](./docs/assets/2025-07-27-demo.mp4)
+Stop getting out-of-date Python package manager commands from your AI. Cross-reference latest official `pip`, `poetry`, `uv`, and `conda` docs with auto-updates. [[Watch Demo on YouTube]](https://youtu.be/3nVp46Q8FdY)
 
 ## 🚀 Quick Start for Agentic IDEs