farmd MVP scaffold: HTTP server, healthz, dashboard placeholder

Go printer-farm manager (Wave 1, Redmine #855). Cloudron-deployable,
OIDC via platform provider planned; Moonraker/OctoPrint/Bambu adapters
+ Dolibarr connector are the next milestones. Dockerfile: multi-stage,
non-root, no Node anywhere in the chain.

internal/server/server.go

@@ -0,0 +1,46 @@
+// Package server wires the HTTP surface: health, dashboard, and (coming)
+// the printer/job APIs. See Redmine #855 for the component design.
+package server
+
+import (
+	"fmt"
+	"html/template"
+	"net/http"
+)
+
+type Config struct {
+	Addr   string
+	DBPath string
+}
+
+type Server struct {
+	cfg Config
+	mux *http.ServeMux
+}
+
+func New(cfg Config) *Server {
+	s := &Server{cfg: cfg, mux: http.NewServeMux()}
+	s.mux.HandleFunc("/healthz", s.health)
+	s.mux.HandleFunc("/", s.index)
+	return s
+}
+
+func (s *Server) Run() error {
+	return http.ListenAndServe(s.cfg.Addr, s.mux)
+}
+
+func (s *Server) health(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, "ok")
+}
+
+// index is the farm dashboard placeholder. The real board (printer cards,
+// job queue, batch view) lands with the printer adapters.
+func (s *Server) index(w http.ResponseWriter, _ *http.Request) {
+	t, err := template.ParseFiles("web/templates/index.html")
+	if err != nil {
+		http.Error(w, "template: "+err.Error(), http.StatusInternalServerError)
+		return
+	}
+	_ = t.Execute(w, map[string]string{"Toolset": "farmd 0.1.0-dev"})
+}