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/ClientApiPersonasTests.cs

@@ -103,7 +103,7 @@ namespace PrivaPub.Tests.Http
 			var response = await Insert(root, new { userName, name = userName, biography = "testing" });
 
 			Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
-			Assert.Contains("already take", (await response.JsonBody())["errorMessage"]!.GetValue<string>());
+			Assert.Contains("already taken", (await response.JsonBody())["errorMessage"]!.GetValue<string>());
 			Assert.Empty(await Listed(root));
 		}