fix: configure Docker containers to run as current user

- Added user mapping (UID:GID) to Docker Compose services to prevent root-owned files
- Export current user's UID/GID in build.sh for Docker Compose
- Enhanced clean build to handle permission issues gracefully:
  * Try normal cleanup first
  * Fallback to container-based cleanup for root-owned files
  * Ultimate fallback to sudo if needed
- Added cleanup for all Docker volumes (build, source, kernel, target caches)

Fixes 'Permission denied' errors when cleaning output files created by Docker containers.

build.sh

@@ -114,17 +114,29 @@ cd "$(dirname "$0")/build"
 if [ "$CLEAN_BUILD" = true ]; then
     print_info "Cleaning build artifacts and cache..."
     
-    # Remove output artifacts
-    rm -rf ../output/*
+    # Remove output artifacts (use sudo if needed for root-owned files)
+    if ! rm -rf ../output/* 2>/dev/null; then
+        print_info "  Some files owned by root, using container to clean..."
+        export UID=$(id -u)
+        export GID=$(id -g)
+        docker compose run --rm builder sh -c "rm -rf /build/output/*" || {
+            print_warning "Failed to clean output directory, trying with sudo"
+            sudo rm -rf ../output/*
+        }
+    fi
     print_info "  Removed output artifacts"
     
     # Remove cache directories
-    rm -rf ../cache/*
+    rm -rf ../cache/* 2>/dev/null || {
+        print_info "  Using sudo to remove cache directories..."
+        sudo rm -rf ../cache/*
+    }
     print_info "  Removed cache directories"
     
     # Remove Docker volumes
     print_info "  Removing Docker cache volumes..."
     docker volume rm alpine-initramfs_github-cache alpine-initramfs_kernel-cache 2>/dev/null || true
+    docker volume rm build_build-cache build_source-cache build_kernel-cache build_target-cache 2>/dev/null || true
     print_info "  Docker cache volumes removed"
     
     print_success "Clean completed successfully"
@@ -138,6 +150,8 @@ mkdir -p ../output ../cache/github ../cache/packages
 export BUILDMODE
 export MINIMAL_MODE
 export TARGETARCH="${TARGETARCH:-amd64}"
+export UID=$(id -u)
+export GID=$(id -g)
 
 if [ "$DEV_MODE" = true ]; then
     print_info "Starting development container..."

build/docker-compose.yml

@@ -12,6 +12,7 @@ services:
     image: zero-os-alpine-builder:cached-${BUILDMODE:-debug}
     container_name: zero-os-alpine-builder-cached
     privileged: true
+    user: "${UID:-1000}:${GID:-1000}"
     volumes:
       # Mount source configs and scripts (read-only for cache efficiency)
       - ../configs:/build/configs:ro
@@ -45,6 +46,7 @@ services:
     image: zero-os-alpine-builder:legacy
     container_name: zero-os-alpine-builder-legacy
     privileged: true
+    user: "${UID:-1000}:${GID:-1000}"
     volumes:
       - ../configs:/build/configs:ro
       - ../scripts:/build/scripts:ro