feat: local device profile replaces animal naming

- Users set their own device name and optional profile photo
- Profile persisted in localStorage, no account needed
- Auto-detect device type from user agent
- Server validates client-provided profile defensively
- PeerAvatar shows photo or device icon
- ProfileSetup modal on first visit, editable from header

server/src/index.ts

@@ -113,14 +113,15 @@ function checkMessageRate(client: Client): boolean {
 }
 
 /** Sanitize client-provided display name */
-function sanitizeName(name: string): string {
+function sanitizeName(name: unknown): string {
+  if (typeof name !== "string") return "Appareil";
   return name.trim().slice(0, 30) || "Appareil";
 }
 
 /** Validate device type */
-function validateDeviceType(dt: string): DeviceType {
+function validateDeviceType(dt: unknown): DeviceType {
   const valid: DeviceType[] = ["phone", "tablet", "laptop", "desktop"];
-  return valid.includes(dt as DeviceType) ? (dt as DeviceType) : "laptop";
+  return typeof dt === "string" && valid.includes(dt as DeviceType) ? (dt as DeviceType) : "laptop";
 }
 
 /** Validate avatar (must be a small data URL or undefined) */