Fix 404s: serve UI templates/static from configurable ui-root, not CWD

The web UI 404'd in production because templates/static were loaded
via relative paths ("internal/ui/templates", "internal/ui/static"),
which only resolved when running from the repo checkout. systemd sets
WorkingDirectory=/var/lib/wireguard-ui-multi, so those paths never
existed there.

Add a -ui-root flag (default /usr/local/share/wireguard-ui-multi/ui),
have install.sh copy internal/ui there, and resolve templates/static
paths through it instead of hardcoded relative strings.

Also add release-binary fast path to bootstrap.sh (falls back to
source build with CGO_ENABLED=0/-trimpath if no release exists yet),
and document real hardware/build-RAM requirements in the README.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/api/router.go

@@ -3,6 +3,7 @@ package api
 import (
 	"log/slog"
 	"net/http"
+	"path/filepath"
 
 	"gitea.perlbach24.de/scripte/wireguard-ui-multi/internal/database"
 	"gitea.perlbach24.de/scripte/wireguard-ui-multi/internal/server"
@@ -15,18 +16,28 @@ type API struct {
 	sessions *SessionStore
 	log      *slog.Logger
 	lanIface string
+	uiRoot   string
 }
 
-func New(db *database.DB, log *slog.Logger, lanIface string) *API {
+func New(db *database.DB, log *slog.Logger, lanIface, uiRoot string) *API {
 	return &API{
 		db:       db,
 		store:    server.NewStore(db),
 		sessions: NewSessionStore(),
 		log:      log,
 		lanIface: lanIface,
+		uiRoot:   uiRoot,
 	}
 }
 
+func (a *API) templatesDir() string {
+	return filepath.Join(a.uiRoot, "templates")
+}
+
+func (a *API) staticDir() string {
+	return filepath.Join(a.uiRoot, "static")
+}
+
 // Routes builds the full HTTP handler tree (API + UI), using Go 1.22 mux patterns.
 func (a *API) Routes() http.Handler {
 	mux := http.NewServeMux()
@@ -57,7 +68,7 @@ func (a *API) Routes() http.Handler {
 	mux.HandleFunc("GET /", a.handleDashboard)
 	mux.HandleFunc("GET /login", a.handleLoginPage)
 	mux.HandleFunc("GET /servers/{id}", a.handleServerPage)
-	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.Dir("internal/ui/static"))))
+	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.Dir(a.staticDir()))))
 
 	return a.logMiddleware(mux)
 }

internal/api/ui_handlers.go

@@ -4,8 +4,6 @@ import (
 	"net/http"
 )
 
-const templatesDir = "internal/ui/templates"
-
 // hasSession reports whether the request carries a valid, non-expired session cookie.
 func (a *API) hasSession(r *http.Request) bool {
 	c, err := r.Cookie(sessionCookieName)
@@ -21,7 +19,7 @@ func (a *API) handleDashboard(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/login", http.StatusFound)
 		return
 	}
-	http.ServeFile(w, r, templatesDir+"/dashboard.html")
+	http.ServeFile(w, r, a.templatesDir()+"/dashboard.html")
 }
 
 func (a *API) handleLoginPage(w http.ResponseWriter, r *http.Request) {
@@ -29,7 +27,7 @@ func (a *API) handleLoginPage(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/", http.StatusFound)
 		return
 	}
-	http.ServeFile(w, r, templatesDir+"/login.html")
+	http.ServeFile(w, r, a.templatesDir()+"/login.html")
 }
 
 func (a *API) handleServerPage(w http.ResponseWriter, r *http.Request) {
@@ -37,5 +35,5 @@ func (a *API) handleServerPage(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/login", http.StatusFound)
 		return
 	}
-	http.ServeFile(w, r, templatesDir+"/server.html")
+	http.ServeFile(w, r, a.templatesDir()+"/server.html")
 }