feat(vision): route multimodal analysis to dedicated NVIDIA direct endpoint

- config: add AI_LLM_VISION_BASE_URL + AI_LLM_VISION_API_KEY (separate from text router)
- llmClient: llmVision() now calls dedicated vision endpoint when configured
  (axios POST to integrate.api.nvidia.com, model nvidia/nemotron-3-nano-omni-30b-a3b-reasoning,
  reasoning_budget 16384, non-stream), falls back to router combo otherwise
- keeps text/moderation on omniroute, vision on NVIDIA direct

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

@@ -137,7 +137,13 @@ export const configSchema = z
       .url()
       .default("https://9router.asepharyana.my.id/v1"),
     AI_LLM_MODEL: z.string().default("text"),
-    AI_LLM_VISION_MODEL: z.string().optional(),
+    AI_LLM_VISION_MODEL: z.string().default("multimodal"),
+    // Vision can be routed to a dedicated endpoint (e.g. NVIDIA direct) that is
+    // separate from the text/moderation router. When both are set, llmVision()
+    // calls the dedicated vision endpoint directly; otherwise it falls back to
+    // the shared AI_LLM_BASE_URL with AI_LLM_VISION_MODEL.
+    AI_LLM_VISION_BASE_URL: z.string().url().optional(),
+    AI_LLM_VISION_API_KEY: z.string().optional(),
     AI_LLM_EMBEDDING_MODEL: z.string().optional(),
     AI_LLM_EMBEDDING_MIN_SIMILARITY: z.coerce
       .number()