Migrate from GitHub to Gitea with CI/CD

- Add Gitea Actions workflow for automated frontend and API deployment
- Update all raw download URLs from GitHub to Gitea
- Remove deprecated Amplify config and GitHub-specific Terraform variables
- Clean up commented-out Amplify resources from Terraform
- Update documentation to reflect new repository and CI/CD setup

terraform/variables.tf

@@ -1,14 +1,3 @@
-variable "github_repository" {
-  description = "GitHub repository URL"
-  type        = string
-}
-
-variable "github_token" {
-  description = "GitHub personal access token for Amplify"
-  type        = string
-  sensitive   = true
-}
-
 variable "domain_name" {
   description = "Custom domain name (optional)"
   type        = string