Say "not available in your country" instead of "relay returned 451"

The edge geo-gate serves US, PE and BO for the relay and accounts hosts, and
answers 451 for anywhere else — before the request reaches the relay. Nothing in
either client knew what 451 meant, so it fell through to the generic branch.

⚠️ **The download site is deliberately not gated**, which makes this worse than
a bad error string. Someone outside those countries can read the page, install
the app, choose a password, tap sign up, and be told "relay returned 451".
Nothing in that mentions their country, and it is not a failure they can retry
past, so the only sensible reading is that the app is broken.

451 is the right status — this is a legal/policy refusal, not a 403 — so the
only thing missing was somebody translating it.

client 96.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/main/kotlin/io/flamenet/client/MessengerApi.kt

@@ -294,6 +294,8 @@ class MessengerApi(
                 401, 403 -> RelayException.Unauthorized(message)
                 404 -> RelayException.NotFound(message.ifBlank { request.url.encodedPath })
                 429 -> RelayException.RateLimited(it.header("Retry-After")?.toIntOrNull())
+                // The geo-gate, not the relay. Needs a sentence, not a number.
+                451 -> RelayException.Unavailable(message)
                 else -> RelayException.Http(it.code, message)
             }
         }

client/src/main/kotlin/io/flamenet/client/RelayAccounts.kt

@@ -133,6 +133,8 @@ class RelayAccounts(
                 404 -> RelayException.NotFound(path)
                 409 -> RelayException.Http(409, message)
                 429 -> RelayException.RateLimited(it.header("Retry-After")?.toIntOrNull())
+                // The geo-gate, not the relay. Needs a sentence, not a number.
+                451 -> RelayException.Unavailable(message)
                 else -> RelayException.Http(it.code, message)
             }
         }

client/src/main/kotlin/io/flamenet/client/RelayClient.kt

@@ -513,6 +513,8 @@ class RelayClient(
             401 -> RelayException.Unauthorized(readable)
             404 -> RelayException.NotFound(path)
             429 -> RelayException.RateLimited(response.header("Retry-After")?.toIntOrNull())
+            // The geo-gate, not the relay. Needs a sentence, not a number.
+            451 -> RelayException.Unavailable(readable)
             else -> RelayException.Http(code, readable)
         }
     }

client/src/main/kotlin/io/flamenet/client/RelayException.kt

@@ -26,6 +26,21 @@ sealed class RelayException(message: String, cause: Throwable? = null) : Excepti
     class RateLimited(val retryAfterSeconds: Int?) :
         RelayException("rate limited" + (retryAfterSeconds?.let { ", retry in ${it}s" } ?: ""))
 
+    /**
+     * 451 — this service is not offered in the caller's country.
+     *
+     * 🔴 **Its own type because the generic one reads as a broken app.** The
+     * edge geo-gate answers 451 before the request reaches the relay, and the
+     * download site is deliberately NOT gated — so somebody can read the page,
+     * install the app, choose a password, tap sign up, and be shown "relay
+     * returned 451". Nothing in that mentions their country, and it is not a
+     * failure they can retry past, so the only sensible reading is that the app
+     * does not work.
+     */
+    class Unavailable(val body: String) : RelayException(
+        "Flamenet isn't available in your country yet. " +
+            "This isn't a problem with your account or your connection.")
+
     /** Any other non-2xx. The body is kept because relays put the reason in it. */
     class Http(val status: Int, val body: String) : RelayException("relay returned $status: $body")
 

client/src/test/kotlin/io/flamenet/client/GeoUnavailableTest.kt

@@ -0,0 +1,33 @@
+package io.flamenet.client
+
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+/**
+ * 451 — the country gate (§ edge policy).
+ *
+ * 🔴 **The download site is deliberately NOT gated.** Someone outside the
+ * served countries can read the page, install the app, choose a password, tap
+ * sign up — and only then does the edge answer 451, before the request ever
+ * reaches the relay. Reported as a status code, that reads as a broken app:
+ * nothing mentions their country, and it is not a failure they can retry past.
+ */
+class GeoUnavailableTest {
+
+    @Test
+    fun `the message names the country, not the status code`() {
+        val message = RelayException.Unavailable("").message.orEmpty()
+        assertTrue("country" in message, "must say why: $message")
+        assertTrue("451" !in message, "a status code explains nothing: $message")
+    }
+
+    /**
+     * ⚠️ It must also say what it is NOT. Someone who has just typed a password
+     * will otherwise assume they got it wrong and try again — and again.
+     */
+    @Test
+    fun `the message rules out the account and the connection`() {
+        val message = RelayException.Unavailable("").message.orEmpty()
+        assertTrue("account" in message && "connection" in message, message)
+    }
+}