fix: Address critical code review feedback from Gemini

CRITICAL FIXES:
1. Restore multi-architecture support - Use ARG BUILD_FROM/BUILD_ARCH instead of hardcoded amd64 base image
   - Fixes: aarch64 builds were broken by hardcoded FROM ghcr.io/hassio-addons/base/amd64:11.1.0
   - Now: FROM $BUILD_FROM allows alexbelgium build system to set correct base per architecture

2. Remove stderr suppression from agent command - Restore error visibility for debugging
   - Fixes: Error messages were hidden by 2>/dev/null redirection
   - Now: ./agent command output visible for user diagnostics

These changes ensure:
- Multi-arch builds work correctly (amd64, aarch64, armv7, armhf, i386)
- Users can debug configuration issues via visible error logs
- Circular dependency fix is fully compatible with existing build system

portainer_agent/Dockerfile

@@ -2,7 +2,9 @@
 # Fix for: FATAL: PROTECTION MODE IS ENABLED! error when protection mode is OFF
 # Approach: Level 1 (standard bashio) + Level 2 (socket fallback)
 
-FROM ghcr.io/hassio-addons/base/amd64:11.1.0
+ARG BUILD_FROM
+ARG BUILD_ARCH
+FROM $BUILD_FROM
 
 # Step 1: Replace bashio v0.17.5 with main branch for improved API error handling
 RUN rm -rf /usr/lib/bashio /usr/bin/bashio && \
@@ -96,7 +98,7 @@ bashio::log.info "Starting Portainer Agent"
 # Launch app
 cd /app || true
 if bashio::config.has_value 'PORTAINER_AGENT_ARGS'; then
-    ./agent "$PORTAINER_AGENT_ARGS" 2> /dev/null
+    ./agent "$PORTAINER_AGENT_ARGS"
 else
     ./agent
 fi