fix(docker): update base image references to Docker Hub

- Changed base image references in `docker-bake.hcl`, Dockerfiles, and `mirror-base-images.sh` from public ECR to Docker Hub to avoid 429 errors and improve reliability.
- Updated README documentation to reflect the new source for base images, clarifying the mirroring process and behavior when tags already exist.

deploy/docker/docker-bake.hcl

@@ -39,11 +39,11 @@ variable "CACHE_REF_BIRDC" {
 }
 
 variable "BASE_GOLANG" {
-  default = "public.ecr.aws/docker/library/golang:1.24-alpine"
+  default = "docker.io/library/golang:1.24-alpine"
 }
 
 variable "BASE_DEBIAN" {
-  default = "public.ecr.aws/docker/library/debian:bookworm-slim"
+  default = "docker.io/library/debian:bookworm-slim"
 }
 
 variable "BASE_DISTROLESS" {
@@ -51,15 +51,15 @@ variable "BASE_DISTROLESS" {
 }
 
 variable "BASE_NODE" {
-  default = "public.ecr.aws/docker/library/node:22-alpine"
+  default = "docker.io/library/node:22-alpine"
 }
 
 variable "BASE_NGINX" {
-  default = "public.ecr.aws/docker/library/nginx:1.27-alpine"
+  default = "docker.io/library/nginx:1.27-alpine"
 }
 
 variable "BASE_UBUNTU" {
-  default = "public.ecr.aws/docker/library/ubuntu:noble"
+  default = "docker.io/library/ubuntu:noble"
 }
 
 function "go-cache-from" {