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/internal/api/calls.go

@@ -0,0 +1,54 @@
+package api
+
+import (
+	"net/http"
+	"strings"
+
+	"smsgateway/apiserver/internal/pb"
+)
+
+type enqueueCallRequest struct {
+	PhoneNumber string `json:"phone_number"`
+	DeviceID    string `json:"device_id"`
+}
+
+// handleEnqueueCall queues an outbound phone call for one of the user's devices.
+// A call is stored as a message with type "call"; the device pulls it through
+// the same mobile pipeline as SMS and places the call natively.
+func (s *Server) handleEnqueueCall(w http.ResponseWriter, r *http.Request) {
+	uid, _ := userFromCtx(r.Context())
+
+	var req enqueueCallRequest
+	if err := decodeJSON(r, &req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	phone := strings.TrimSpace(req.PhoneNumber)
+	if phone == "" {
+		writeError(w, http.StatusBadRequest, "phone_number is required")
+		return
+	}
+
+	deviceRecID, err := s.resolveDevice(r, uid, req.DeviceID)
+	if err != nil {
+		writeUpstreamError(w, err)
+		return
+	}
+	if deviceRecID == "" {
+		writeError(w, http.StatusBadRequest, "no device available; register a device first")
+		return
+	}
+
+	rec, err := s.pb.Create(r.Context(), colMessages, pb.Record{
+		"phone_numbers": []string{phone},
+		"type":          msgTypeCall,
+		"device":        deviceRecID,
+		"owner":         uid,
+		"status":        statusPending,
+	})
+	if err != nil {
+		writeUpstreamError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusAccepted, recordToMessage(rec))
+}