feat: remove start.sh script and add appearance preferences management

- Deleted the start.sh script for container management.
- Added AGENTS.md for project guidelines and development principles.
- Introduced new SQL migration files for user appearance preferences and platform settings.
- Implemented appearance provider to manage user interface themes and preferences.
- Created branding utility to define and manage branding-related constants and types.

Co-authored-by: Copilot <copilot@github.com>

.gitignore

@@ -34,6 +34,7 @@ yarn-error.log*
 # local env files
 # do not commit any .env files to git, except for the .env.example file. https://create.t3.gg/en/usage/env-variables#using-environment-variables
 .env
+.env.prod
 .env*.local
 .env*.production
 
@@ -41,4 +42,4 @@ yarn-error.log*
 *.tsbuildinfo
 
 # idea files
-.idea
+.idea