fix(lotus): explain a failed voice connection and offer Try again

"Failed to connect to Livekit server (Reason: ServerUnreachable)" left a
user with nothing to try; they retried for a long time and gave up.

- Title "Couldn't connect to voice". The message depends on the reason:
  unreachable/timeout-style errors explain that voice needs its own live
  connection, which VPNs, antivirus web shields and some networks block,
  even when chat works, and say what to try; NotAllowed says the call may
  be full or access changed.
- The raw reason, status and message move under Technical details.
- LivekitConnectionError and PeerConnectionTimeoutError now get a
  Try again button (the existing reconnect path), shown as primary: the
  Lotus theme renders `secondary` as dark-on-dark.

Verified in the Lotus client against a local LiveKit with the signal
socket and validate request blocked: the dialog appears after ~20 s;
unblocking and pressing Try again joins with the mic published.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/utils/errors.ts

@@ -6,7 +6,7 @@ Please see LICENSE in the repository root for full details.
 */
 
 import { t } from "i18next";
-import { type ConnectionError } from "livekit-client";
+import { type ConnectionError, ConnectionErrorReason } from "livekit-client";
 
 import { i18nKey } from "./i18n";
 
@@ -53,6 +53,9 @@ export class ElementCallError extends Error {
   public localisedMessageKey?: string;
   public localisedMessageValues?: Record<string, string>;
 
+  /** [lotus] Raw detail shown under a collapsed "Technical details", not in the message. */
+  public technicalDetails?: string;
+
   protected constructor(
     localisedTitle: string,
     code: ErrorCode,
@@ -307,9 +310,21 @@ export class LivekitConnectionError extends ElementCallError {
       ErrorCode.SFU_ERROR,
       ErrorCategory.NETWORK_CONNECTIVITY,
     );
-    this.localisedMessageKey = i18nKey(
-      "error.livekit_connection_error_description",
-    );
+    // [lotus] "An error occurred while connecting to the Livekit server
+    // (Reason: ServerUnreachable)" left people with nothing to try (Gitea
+    // element-call: a friend retried for ages while Element worked). Say what
+    // it means and what to do; keep the raw reason under Technical details.
+    this.localisedMessageKey =
+      cause.reason === ConnectionErrorReason.NotAllowed
+        ? i18nKey("error.livekit_not_allowed_description")
+        : i18nKey("error.livekit_unreachable_description");
     this.localisedMessageValues = { reason: cause.reasonName };
+    this.technicalDetails = [
+      `Reason: ${cause.reasonName}`,
+      cause.status ? `Status: ${cause.status}` : null,
+      cause.message,
+    ]
+      .filter(Boolean)
+      .join("\n");
   }
 }