feat(deployment): replace monster scripts with modular helper scripts (#87)

- Add install.sh orchestrator with upgrade support
- Add 6 helper scripts (<100 lines each) replacing 700-800 line monsters
- Add deployment/linux/furt.service systemd template
- Support both fresh install and upgrade modes
- Platform-aware detection (OpenBSD/FreeBSD vs Linux)
- Skip user/service creation in upgrade mode
- Preserve existing configuration during updates
- Remove merkwerk dependency from production install script

Helper scripts:
- scripts/setup-user.sh - Create system user (_furt/furt)
- scripts/setup-directories.sh - Create directory structure
- scripts/sync-files.sh - Copy source files to installation
- scripts/create-service.sh - Create system service from templates
- scripts/validate-config.sh - Validate furt.conf syntax
- scripts/health-check.sh - Basic health check functionality

Closes DAW/furt#87

scripts/sync-files.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+# scripts/sync-files.sh - Copy furt source files to installation directory
+
+set -e
+
+# Check if we're in a furt source directory
+if [ ! -f "src/main.lua" ]; then
+    echo "Error: Not in furt source directory (src/main.lua not found)"
+    exit 1
+fi
+
+# Target directory
+TARGET="/usr/local/share/furt"
+
+echo "Copying furt files to $TARGET..."
+
+# Copy main directories
+cp -r src/ "$TARGET/"
+cp -r config/ "$TARGET/"
+cp -r scripts/ "$TARGET/"
+cp -r integrations/ "$TARGET/"
+
+# Copy version files for merkwerk integration
+[ -f "VERSION" ] && cp VERSION "$TARGET/"
+[ -f ".version_history" ] && cp .version_history "$TARGET/"
+
+# Set proper permissions
+chown -R root:wheel "$TARGET" 2>/dev/null || chown -R root:root "$TARGET"
+chmod -R 644 "$TARGET"
+find "$TARGET" -type d -exec chmod 755 {} \;
+chmod +x "$TARGET/scripts/start.sh"
+
+echo "Files synced successfully to $TARGET"
+