fix: restrict proxy content access and scope backup storage to owners

- Hide proxy configuration contents from users without update permission.
- Select and validate backup S3 storage against the resource's team.
- Keep scheduled branch syncs green while a conflict PR remains open.
- Document external mount permissions and Sentinel traffic limits.
- Add regression coverage for authorization and backup storage selection.

tests/Unit/RemoteOutputSizeLimitsTest.php

@@ -32,6 +32,7 @@ function remoteOutputTestServer(): Server
 it('bounds dynamic proxy configuration files and their combined Livewire payload', function () {
     $server = Mockery::mock(remoteOutputTestServer())->makePartial();
     $server->shouldReceive('proxyPath')->andReturn('/data/proxy');
+    $this->actingAs(User::query()->latest('id')->firstOrFail());
     $files = collect(range(1, 101))->map(fn (int $number) => sprintf('file%03d.yml', $number))->implode("\n");
 
     Process::fake(function ($process) use ($files) {