feat: Implement precise Docker build triggering using workflow_run event (#233)

* fix: correct YAML indentation error in docker workflow

- Fix incorrect indentation at line 237 in .github/workflows/docker.yml
- Step 'Extract metadata and generate tags' had 12 spaces instead of 6
- This was causing YAML syntax validation to fail

* fix: restore unified build-rustfs task with correct YAML syntax

- Revert complex job separation back to single build-rustfs task
- Maintain Linux and macOS builds in unified matrix
- Fix YAML indentation and syntax issues
- Docker builds will use only Linux binaries as designed in Dockerfile

* feat: implement precise Docker build triggering using workflow_run

- Use workflow_run event to trigger Docker builds independently
- Add precise Linux build status checking via GitHub API
- Only trigger Docker builds when both Linux architectures succeed
- Remove coupling between build.yml and docker.yml workflows
- Improve TARGETPLATFORM consistency in Dockerfile

This resolves the issue where Docker builds would trigger even if
Linux ARM64 builds failed, causing missing binary artifacts during
multi-architecture Docker image creation.

Dockerfile

@@ -1,8 +1,9 @@
 # Multi-stage build for RustFS production image
 FROM alpine:latest AS build
 
-# Build arguments
-ARG TARGETARCH
+# Build arguments - use TARGETPLATFORM for consistency with Dockerfile.source
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
 ARG RELEASE=latest
 ARG CHANNEL=release
 
@@ -18,11 +19,11 @@ RUN apk add --no-cache \
 # Create build directory
 WORKDIR /build
 
-# Map TARGETARCH to architecture format used in builds
-RUN case "${TARGETARCH}" in \
-        "amd64") ARCH="x86_64" ;; \
-        "arm64") ARCH="aarch64" ;; \
-        *) echo "Unsupported architecture: ${TARGETARCH}" && exit 1 ;; \
+# Map TARGETPLATFORM to architecture format used in builds
+RUN case "${TARGETPLATFORM}" in \
+        "linux/amd64") ARCH="x86_64" ;; \
+        "linux/arm64") ARCH="aarch64" ;; \
+        *) echo "Unsupported platform: ${TARGETPLATFORM}" && exit 1 ;; \
     esac && \
     echo "ARCH=${ARCH}" > /build/arch.env