chore: clean up project root

- Delete demo.mp4 (stale, replaced by gif)
- Move demo.gif to hack/ alongside demo.tape
- Update README and demo.tape to reference new path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: marzagao

README.md

@@ -3,7 +3,7 @@
 Monitor and control your reef aquarium from the terminal — all on your local network, no cloud required.
 
 [![Go](https://img.shields.io/badge/Go-1.25+-00ADD8?logo=go)](https://go.dev) [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE) [![CI](https://github.com/marzagao/aquadirector/actions/workflows/ci.yml/badge.svg)](https://github.com/marzagao/aquadirector/actions/workflows/ci.yml) [![Go Report Card](https://goreportcard.com/badge/github.com/marzagao/aquadirector)](https://goreportcard.com/report/github.com/marzagao/aquadirector)
-![Demo](demo.gif)
+![Demo](hack/demo.gif)
 
 ## Supported Devices
 

demo.mp4

@@ -9,10 +9,10 @@
 # Generate (run from repo root):
 #   CHROMIUM_PATH="/Applications/Google Chrome.app/Contents/MacOS/Google Chrome" vhs hack/demo.tape
 #
-# Output: demo.gif — add to README with:
-#   ![Demo](demo.gif)
+# Output: hack/demo.gif — add to README with:
+#   ![Demo](hack/demo.gif)
 
-Output demo.gif
+Output hack/demo.gif
 
 Set Shell "bash"
 Set FontSize 10