fix: route providers through correct APIs (#39)

Providers with known public APIs use their official endpoints:
- meta-llama → api.llama.com/v1
- microsoft → models.inference.ai.azure.com (GitHub Models)
- ibm-granite → us-south.ml.cloud.ibm.com/ml/v1 (watsonx)
- tencent → api.hunyuan.cloud.tencent.com/v1
- morph → api.morphllm.com/v1

16 remaining providers without known public APIs route through
OpenRouter (base_url = openrouter.ai/api/v1, OPENROUTER_API_KEY).

sync-pricing.py updated with PROVIDER_API mapping.

providers/microsoft.toml

@@ -3,8 +3,8 @@
 [provider]
 id = "microsoft"
 display_name = "Microsoft"
-api_key_env = "OPENROUTER_API_KEY"
-base_url = "https://openrouter.ai/api/v1"
+api_key_env = "GITHUB_TOKEN"
+base_url = "https://models.inference.ai.azure.com"
 key_required = true
 
 [[models]]