fix: service restart on upgrade and no-cache headers for SPA assets

- postinst: restart instead of start if service already enabled (upgrade case)
- embed.go: no-cache/no-store on index.html, immutable cache on hashed assets
- Fixes web not refreshing after dpkg upgrade

Makefile

@@ -33,7 +33,7 @@ package: build-all
 	cp etc/syncserver/config.yaml dist/deb/etc/syncserver/config.yaml
 	cp lib/systemd/system/$(BINARY).service dist/deb/lib/systemd/system/$(BINARY).service
 	printf 'Package: $(BINARY)\nVersion: $(VERSION)\nSection: net\nPriority: optional\nArchitecture: amd64\nDepends: rsync, openssh-client, ca-certificates\nMaintainer: SyncServer\nDescription: File sync orchestrator with Wake-on-LAN and web UI\n' > dist/deb/DEBIAN/control
-	printf '#!/bin/sh\nset -e\nid $(BINARY) >/dev/null 2>&1 || useradd --system --no-create-home --shell /usr/sbin/nologin $(BINARY)\ninstall -d -o $(BINARY) -g $(BINARY) -m 0750 /var/lib/$(BINARY)/data\ninstall -d -o $(BINARY) -g $(BINARY) -m 0750 /var/lib/$(BINARY)/ssh\ninstall -d -o $(BINARY) -g $(BINARY) -m 0750 /var/lib/$(BINARY)/logs\ninstall -d -o root -g root -m 0755 /etc/$(BINARY)\n[ ! -f /etc/$(BINARY)/config.yaml ] && cp /etc/$(BINARY)/config.yaml /etc/$(BINARY)/config.yaml.new || true\nsystemctl daemon-reload 2>/dev/null || true\nsystemctl enable --now $(BINARY).service 2>/dev/null || true\n' > dist/deb/DEBIAN/postinst
+	printf '#!/bin/sh\nset -e\nSVC=$(BINARY)\nid $$SVC >/dev/null 2>&1 || useradd --system --no-create-home --shell /usr/sbin/nologin $$SVC\ninstall -d -o $$SVC -g $$SVC -m 0750 /var/lib/$$SVC/data\ninstall -d -o $$SVC -g $$SVC -m 0750 /var/lib/$$SVC/ssh\ninstall -d -o $$SVC -g $$SVC -m 0750 /var/lib/$$SVC/logs\ninstall -d -o root -g root -m 0755 /etc/$$SVC\n[ ! -f /etc/$$SVC/config.yaml ] && cp /etc/$$SVC/config.yaml /etc/$$SVC/config.yaml.new || true\nsystemctl daemon-reload 2>/dev/null || true\nif systemctl is-enabled --quiet $$SVC.service 2>/dev/null; then\n\tsystemctl restart $$SVC.service 2>/dev/null || true\nelse\n\tsystemctl enable --now $$SVC.service 2>/dev/null || true\nfi\n' > dist/deb/DEBIAN/postinst
 	chmod 0755 dist/deb/DEBIAN/postinst
 	printf '#!/bin/sh\nset -e\nsystemctl stop $(BINARY).service 2>/dev/null || true\nsystemctl disable $(BINARY).service 2>/dev/null || true\n' > dist/deb/DEBIAN/prerm
 	chmod 0755 dist/deb/DEBIAN/prerm

internal/webui/embed.go

@@ -16,6 +16,7 @@ func ServeHTTP() http.Handler {
 }
 
 func ServeSPA() http.Handler {
+	fsHandler := http.FileServer(http.FS(distSub))
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		path := r.URL.Path
 		if path == "/favicon.ico" {
@@ -28,11 +29,15 @@ func ServeSPA() http.Handler {
 				http.Error(w, "not found", http.StatusNotFound)
 				return
 			}
-			w.Header().Set("Content-Type", "text/html")
+			w.Header().Set("Content-Type", "text/html; charset=utf-8")
+			w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+			w.Header().Set("Pragma", "no-cache")
+			w.Header().Set("Expires", "0")
 			w.Write(data)
 			return
 		}
-		http.FileServer(http.FS(distSub)).ServeHTTP(w, r)
+		w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+		fsHandler.ServeHTTP(w, r)
 	})
 }
 

packaging/debian/DEBIAN/postinst

@@ -35,8 +35,11 @@ EOF
 
         if command -v systemctl > /dev/null 2>&1; then
             systemctl daemon-reload 2>/dev/null || true
-            systemctl enable syncserver.service 2>/dev/null || true
-            systemctl start syncserver.service 2>/dev/null || true
+            if systemctl is-enabled --quiet syncserver.service 2>/dev/null; then
+                systemctl restart syncserver.service 2>/dev/null || true
+            else
+                systemctl enable --now syncserver.service 2>/dev/null || true
+            fi
         fi
         ;;