Replace gitea references with GitHub

Point the Quick Start clone command at the GitHub repo and drop the
obsolete .gitea-token ignore rule in favour of a generic secrets pattern.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -17,8 +17,9 @@ __pycache__/
 .claude/
 CLAUDE.md
 
-# Gitea token
-.gitea-token
+# Local secrets / tokens
+*.token
+.git-credentials
 
 # OS
 .DS_Store

README.md

@@ -39,7 +39,7 @@ Draw and edit aircraft sprites directly in the browser: pencil, eraser, line/rec
 
 ```bash
 # Clone the repository
-git clone https://gitea.chops.one/allen/ADS-Bit.git
+git clone https://github.com/AllenNPIT/ADS-Bit.git
 cd ADS-Bit
 
 # Install dependencies