fix(sprint-5/etapa-4f): || fallback en name vacío — botón Guardar habilitado cuando Google devuelve full_name: ""

El operador ?? solo hace fallback con null/undefined, no con cadena vacía.
Si Google devuelve user_metadata.full_name: "", la cadena de propagación es:
  buildAuthUser → name=""  →  upsertUserOnLogin inserta ""  →  syncProfileFromDB
  devuelve ""  →  AuthContext setUser → "" ?? prev.name = ""  →  ProfileSheet
  setName("") → name.trim() === '' → botón disabled → click no hace nada.

Fix: cambiar ?? por || en todos los puntos donde full_name o name de DB
se propagan al estado: buildAuthUser, syncProfileFromDB, getUserFromStorage,
useEffect IIFE en AuthContext. Agregar fallback a email en ProfileSheet
setName() para usuarios cuya fila en DB ya tiene name="" de sesiones anteriores.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/auth/AuthContext.tsx

@@ -30,7 +30,7 @@ function getUserFromStorage(): AuthUser | null {
     return {
       id: u.id as string,
       email,
-      name: (u.user_metadata?.full_name as string) ?? email,
+      name: (u.user_metadata?.full_name as string | undefined) || email,
       avatarUrl: u.user_metadata?.avatar_url as string | undefined,
       platformRole: email.endsWith('@inquality.com.py') ? 'platform_admin' : 'guest',
     }
@@ -95,7 +95,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
         if (profile) {
           setUser((prev) =>
             prev?.id === userId
-              ? { ...prev, company: profile.company, name: profile.name ?? prev.name }
+              ? { ...prev, company: profile.company, name: profile.name || prev.name }
               : prev
           )
         }

src/auth/SupabaseAuthService.ts

@@ -65,7 +65,7 @@ export class SupabaseAuthService implements AuthService {
     const { data } = await (signal ? base.abortSignal(signal) : base).maybeSingle()
     if (!data) return null
     return {
-      name: (data.name as string | null) ?? undefined as unknown as string,
+      name: ((data.name as string | null | undefined) || undefined) as unknown as string,
       company: (data.company as string | null) ?? undefined,
     }
   }
@@ -94,7 +94,7 @@ export class SupabaseAuthService implements AuthService {
     return {
       id: supabaseUser.id,
       email,
-      name: supabaseUser.user_metadata?.full_name as string ?? email,
+      name: (supabaseUser.user_metadata?.full_name as string | undefined) || email,
       avatarUrl: supabaseUser.user_metadata?.avatar_url as string ?? undefined,
       platformRole: email.endsWith('@inquality.com.py') ? 'platform_admin' : 'guest',
     }