A login's storage is counted, and can have a quota

MediaAttachment.Size was stored and never summed: nobody, the administrator included, could tell what media took,
and nothing bounded it. Counted.Media and MediaOfRoot sum what is kept (not trashed). A login sees what its personas'
uploads and pictures take at /clientapi/user/storage (ViewStorage), with its quota when the server sets one;
Media:QuotaBytesPerRoot (0, no quota, by default) refuses an upload or a picture over it with 422, whichever persona
sends it; the statistics overview gains the media totals, the proxy cache and the trash (ViewMediaTotals). Tests: a
login's storage counts what its personas keep and forgets what is trashed; two uploads from two personas of one login
are refused together past the quota.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub.Tests/Domain/MediaFlowTests.cs

@@ -100,6 +100,31 @@ namespace PrivaPub.Tests.Domain
 			Assert.Null(tampered);
 		}
 
+		// a login over its quota uploads nothing more, whichever persona tries
+		[Fact]
+		public async Task A_login_over_its_quota_uploads_nothing_more()
+		{
+			var token = TestContext.Current.CancellationToken;
+			var (root, alice) = await _harness.Persona("alice");
+			var (_, sibling) = await _harness.Persona("sibling", root);
+			var quota = new MediaService(new StaticOptions<MediaOptions>(new MediaOptions { Root = _harness.Media.Root, QuotaBytesPerRoot = 3000 }),
+				_harness.Local, default, Microsoft.Extensions.Logging.Abstractions.NullLogger<MediaService>.Instance);
+			// noise: its PNG is about as big as its pixels, so two of them are over the quota and one is not
+			static byte[] Noise()
+			{
+				var pixels = new byte[30 * 20 * 3];
+				Random.Shared.NextBytes(pixels);
+				using var image = NetVips.Image.NewFromMemory(pixels, 30, 20, 3, NetVips.Enums.BandFormat.Uchar);
+				return image.WriteToBuffer(".png");
+			}
+
+			Assert.True((await quota.Upload(alice, Upload(Noise(), "image/png"), default, default, false, token)).Ok);
+			var full = await quota.Upload(sibling, Upload(Noise(), "image/png"), default, default, false, token);
+
+			Assert.False(full.Ok);
+			Assert.Contains("storage is full", full.Error);
+		}
+
 		// nothing of a suspended server, or of one whose media are rejected, is proxied; blocking one purges what was cached
 		[Fact]
 		public async Task A_blocked_servers_media_are_not_proxied_and_their_cache_goes()