feat(ai): make standalone image/vision analysis timeout explicit (1 min)

The standalone image analysis path (analyzeSingleMediaImage → llmVision →
llmChat) previously had no request-level timeout of its own — it silently
inherited the shared OpenAI client default (60s), and AI_LLM_MEDIA_ANALYSIS_
TIMEOUT_MS only governed the text+media *batch*, not a single vision call.

- Add AI_LLM_VISION_ANALYSIS_TIMEOUT_MS (default 60000) to config.
- llmChat now accepts an optional per-request `timeout` in LlmCallOpts,
  forwarded to the OpenAI request options (falls back to the 60s client
  default when omitted).
- llmVision passes config.AI_LLM_VISION_ANALYSIS_TIMEOUT_MS, so a single
  image/sticker/emoji analysis gets a guaranteed 1-minute budget and is
  independently tunable from the text path.

Verified: tsc + biome green, 129 gateway tests pass.

Co-Authored-By: Claude Opus 5 (Nous Research)

services/discord-gateway/src/shared/config/index.ts

@@ -189,6 +189,15 @@ export const configSchema = z
       .int()
       .positive()
       .default(60000),
+    // Standalone image/sticker/emoji vision analysis (analyzeSingleMediaImage
+    // → llmVision → llmChat). Decoupled from the media *batch* timeout above so
+    // a single vision call can be tuned independently. 1 minute by default —
+    // vision models (especially behind a router) need headroom for large images.
+    AI_LLM_VISION_ANALYSIS_TIMEOUT_MS: z.coerce
+      .number()
+      .int()
+      .positive()
+      .default(60000),
     // Text-only moderation batches are cheaper than media (no downloads /
     // vision pre-pass), so they get their own (shorter) timeout instead of
     // being tied to the media budget.