feat(discord-gateway): use Discord CDN for image analysis, uploader archive-only

- mediaDownloader: flip URL candidate order so discord_url is tried
  before uploaded_url (uploaded_url is archive-only fallback)
- ai-analysis-worker: remove upload-pending race guard that blocked
  analysis until Tele upload completed; analysis now runs immediately
  on the Discord CDN URL
- batchProcessor: remove upload-pending defer/poll-backoff logic
- individualFallbackProcessor: remove upload_pending requeue loop
- batchOutcomeClassifier/fallbackResultClassifier: drop upload_pending
  classification (no longer needed)
- tests: update batchOutcomeClassifier + fallbackResultClassifier tests
  to reflect removed upload_pending signal

services/discord-gateway/tests/fallbackResultClassifier.test.ts

@@ -1,23 +1,12 @@
 // ═══════════════════════════════════════════════════════════════════════════
-// classifyIndividualWorkerResult — upload-pending vs success vs incomplete vs error
-// ═══════════════════════════════════════════════════════════════════════════
-// Bug (2026-08-24): the worker's upload-pending race guard returned
-// {ok:true, results:[]}; the processor treated it as a completed moderation,
-// leaving messages stuck in `processing` until the 300s cleanup reverted them.
+// classifyIndividualWorkerResult — success vs incomplete vs error
+//
+// Upload-pending race guard removed (2026-08-28): analysis no longer
+// depends on the Tele uploader, so there is no upload_pending signal.
 import { describe, expect, it } from "vitest";
 import { classifyIndividualWorkerResult } from "../src/modules/ai-moderation/fallbackResultClassifier.js";
 
 describe("classifyIndividualWorkerResult", () => {
-  it("classifies the upload-pending race guard signal FIRST", () => {
-    expect(
-      classifyIndividualWorkerResult({
-        ok: true,
-        results: [],
-        uploadPending: true,
-      }),
-    ).toBe("upload_pending");
-  });
-
   it("classifies a normal verdict as success", () => {
     expect(
       classifyIndividualWorkerResult({