feat(server): add Dockerfile.fast and scripts for fast host-compiled builds

- Add Dockerfile.fast which packages a pre-built binary instead of compiling inside the container.
- Add scripts/build-fast.ps1 (PowerShell) and scripts/build-fast.sh (Bash) to automate local cross-compilation (CGO_ENABLED=0 GOOS=linux) and Docker packaging.
- Set executable bit for build-fast.sh.

server/scripts/build-fast.ps1

@@ -0,0 +1,49 @@
+# PowerShell script for fast Docker build using host compilation
+param (
+    [string]$Arch = "arm64",
+    [string]$Tag = "x0gp-server:latest"
+)
+
+$ErrorActionPreference = "Stop"
+
+# Navigate to the server root directory if not already there
+$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
+$ServerDir = Split-Path -Parent $ScriptDir
+Push-Location $ServerDir
+
+try {
+    Write-Host "Building Go binary for OS=linux, ARCH=$Arch..." -ForegroundColor Cyan
+    
+    # Setup temporary binary path
+    $BinPath = "bin/poc-server-linux-$Arch"
+    if (!(Test-Path "bin")) {
+        New-Item -ItemType Directory -Path "bin" | Out-Null
+    }
+    
+    # Configure cross-compilation environment variables
+    $env:CGO_ENABLED = "0"
+    $env:GOOS = "linux"
+    $env:GOARCH = $Arch
+    
+    # Compile
+    go build -ldflags="-s -w" -o $BinPath ./cmd/poc-server
+    
+    Write-Host "Go binary successfully compiled: $BinPath" -ForegroundColor Green
+    Write-Host "Building Docker image '$Tag'..." -ForegroundColor Cyan
+    
+    # Run docker build
+    docker build --build-arg BINARY_PATH=$BinPath -t $Tag -f Dockerfile.fast .
+    
+    Write-Host "`nDocker image '$Tag' built successfully!" -ForegroundColor Green
+}
+catch {
+    Write-Host "Error occurred: $_" -ForegroundColor Red
+    exit 1
+}
+finally {
+    # Restore environment variables
+    Remove-Item env:CGO_ENABLED -ErrorAction SilentlyContinue
+    Remove-Item env:GOOS -ErrorAction SilentlyContinue
+    Remove-Item env:GOARCH -ErrorAction SilentlyContinue
+    Pop-Location
+}

server/scripts/build-fast.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Bash script for fast Docker build using host compilation
+
+set -e
+
+ARCH=${1:-"arm64"}
+TAG=${2:-"x0gp-server:latest"}
+
+# Navigate to the server root directory
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SERVER_DIR="$(dirname "$SCRIPT_DIR")"
+cd "$SERVER_DIR"
+
+echo "Building Go binary for OS=linux, ARCH=${ARCH}..."
+mkdir -p bin
+BIN_PATH="bin/poc-server-linux-${ARCH}"
+
+# Compile locally
+CGO_ENABLED=0 GOOS=linux GOARCH=${ARCH} go build -ldflags="-s -w" -o "${BIN_PATH}" ./cmd/poc-server
+
+echo "Go binary successfully compiled: ${BIN_PATH}"
+echo "Building Docker image '${TAG}'..."
+
+# Build docker image
+docker build --build-arg BINARY_PATH="${BIN_PATH}" -t "${TAG}" -f Dockerfile.fast .
+
+echo -e "\nDocker image '${TAG}' built successfully!"