Follow requests asked again, and followed accounts found by name

A server can take a Follow with 202 and drop it afterwards, as Pleroma does
while it cannot fetch our actor; the request then stayed pending for good.
Following again now sends an unanswered request once more, the same
activity, at most once an hour (a delivery's `again` key).

accounts/search takes following=true: only accounts the persona follows,
by the start of their name, display name or server, never resolved; a
client fills a list with it. "already take" becomes "already taken".

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

PrivaPub.Tests/Http/MastodonAccountsTests.cs

@@ -493,6 +493,23 @@ namespace PrivaPub.Tests.Http
 			Assert.All(answer.Array, r => Assert.False(r.Flag("following") || r.Flag("blocking") || r.Flag("muting") || r.Flag("followed_by")));
 		}
 
+		[Fact]
+		public async Task Following_again_sends_an_unanswered_request_once_more_and_no_more_than_hourly()
+		{
+			var since = DateTime.UtcNow.AddSeconds(-1);
+			var alice = await _host.Mastodon("alice");
+			var (bob, bobId) = await Remote();
+			Assert.True((await alice.Client.Post($"/api/v1/accounts/{bobId}/follow")).Ok().Body.Flag("requested"));
+			var first = Assert.Single(await bob.Delivered(since), d => d.Type() == "Follow");
+
+			Assert.True((await alice.Client.Post($"/api/v1/accounts/{bobId}/follow")).Ok().Body.Flag("requested"));
+			(await alice.Client.Post($"/api/v1/accounts/{bobId}/follow")).Ok();
+
+			var follows = (await bob.Delivered(since)).Where(d => d.Type() == "Follow").ToList();
+			Assert.Equal(2, follows.Count);
+			Assert.All(follows, f => Assert.Equal(first.Text("id"), f.Text("id")));
+		}
+
 		[Fact]
 		public async Task A_remote_authors_followers_only_posts_show_only_to_the_personas_that_follow_them()
 		{