Rebrand CommGate to gsmnode and adopt new design system

Rename the whole project from CommGate to gsmnode and re-skin every
surface onto the new signal-green + ink design system (Space Grotesk /
IBM Plex Sans / JetBrains Mono, flat surfaces, two-arrow routing mark,
lowercase gsm+node wordmark).

- Web App + API panel: rewrite token layer, gn-* utilities, data-gsm-theme,
  new logo/favicon assets; both builds verified.
- Phone App (Flutter): green theme, new mark/wordmark widgets, adaptive
  launcher icons; rename Android applicationId/package to app.gsmnode.phone;
  bump AGP to 8.6.0 and google_fonts to 8.1.0; debug APK build verified.
- API Server (Go): panel routes, User-Agent, health service id, branding.
- Home Assistant Plugin: rename integration domain sms_gateway to gsmnode
  (folder, DOMAIN, services, entity ids, classes); py_compile verified.
- Update all READMEs; add .gitignore (excludes Design/, build artifacts).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API Server/cmd/server/main.go

@@ -0,0 +1,64 @@
+// Command server runs the gsmnode API Server. It is the single trusted
+// entry point in front of PocketBase: the Web App and Phone App talk only to
+// this service, which in turn performs all PocketBase access.
+package main
+
+import (
+	"context"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"smsgateway/apiserver/internal/api"
+	"smsgateway/apiserver/internal/auth"
+	"smsgateway/apiserver/internal/config"
+	"smsgateway/apiserver/internal/pb"
+)
+
+func main() {
+	log.SetFlags(log.LstdFlags | log.Lmsgprefix)
+	log.SetPrefix("[api] ")
+
+	cfg := config.Load()
+
+	client := pb.New(cfg.PocketBaseURL, cfg.PBAdminEmail, cfg.PBAdminPass)
+	jwtMgr := auth.NewManager(cfg.JWTSecret, cfg.JWTAccessTTL)
+	srv := api.New(cfg, client, jwtMgr)
+
+	// Background worker that fails messages no device processed in time.
+	workerCtx, workerCancel := context.WithCancel(context.Background())
+	defer workerCancel()
+	srv.StartExpiryWorker(workerCtx)
+
+	httpServer := &http.Server{
+		Addr:              cfg.Addr,
+		Handler:           srv.Handler(),
+		ReadHeaderTimeout: 10 * time.Second,
+		WriteTimeout:      30 * time.Second,
+		IdleTimeout:       60 * time.Second,
+	}
+
+	go func() {
+		log.Printf("listening on %s (PocketBase: %s)", cfg.Addr, cfg.PocketBaseURL)
+		if err := httpServer.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			log.Fatalf("server error: %v", err)
+		}
+	}()
+
+	// Graceful shutdown.
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, os.Interrupt, syscall.SIGTERM)
+	<-stop
+	log.Println("shutting down...")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	if err := httpServer.Shutdown(ctx); err != nil {
+		log.Printf("shutdown error: %v", err)
+	}
+	log.Println("stopped")
+}