fix: clean up OpenRouter-generated provider configs (#37)

- Merge unique models from duplicate providers into their hand-written
  counterparts and remove the duplicates:
  - alibaba (tongyi-deepresearch) → qwen
  - amazon (nova-2-lite, nova-micro, nova-premier) → bedrock
  - bytedance (ui-tars) → volcengine
  - nvidia (nemotron-3-nano, nemotron-3-super, etc.) → nvidia-nim
  - rekaai (reka-flash-3) → reka
- Set correct official API base_url for providers with public APIs:
  arcee-ai, inception, morph, reka, upstage
- Set key_required=false for 20 providers only accessible through
  hosting platforms (no public API)
- Update sync-pricing.py with SKIP_DUPLICATES, PROVIDER_API mapping,
  and default key_required=false for future auto-generated providers

providers/upstage.toml

@@ -4,7 +4,7 @@
 id = "upstage"
 display_name = "Upstage"
 api_key_env = "UPSTAGE_API_KEY"
-base_url = ""
+base_url = "https://api.upstage.ai/v1"
 key_required = true
 
 [[models]]