feat: add avatar field to user profile schema and update related mutations and queries

- Introduced an optional avatar field in the user profile schema to store the URL of the generated avatar.
- Updated the atualizarPerfil mutation to handle the new avatar field.
- Modified the obterPerfil and listarParaChat queries to include the avatar field in the returned user data.

packages/backend/convex/schema.ts

@@ -537,6 +537,7 @@ export default defineSchema({
     // Campos de Chat e Perfil
 
     fotoPerfil: v.optional(v.id("_storage")),
+    avatar: v.optional(v.string()), // URL do avatar gerado (ex: DiceBear)
     setor: v.optional(v.string()),
     statusMensagem: v.optional(v.string()), // max 100 chars
     statusPresenca: v.optional(