feat!: standardize base_url for inference (#4177)

# What does this PR do?

Completes #3732 by removing runtime URL transformations and requiring
users to provide full URLs in configuration. All providers now use
'base_url' consistently and respect the exact URL provided without
appending paths like /v1 or /openai/v1 at runtime.

BREAKING CHANGE: Users must update configs to include full URL paths
(e.g., http://localhost:11434/v1 instead of http://localhost:11434).

Closes #3732 

## Test Plan

Existing tests should pass even with the URL changes, due to default
URLs being altered.

Add unit test to enforce URL standardization across remote inference
providers (verifies all use 'base_url' field with HttpUrl | None type)

Signed-off-by: Charlie Doern <cdoern@redhat.com>

src/llama_stack/distributions/starter-gpu/run-with-postgres-store.yaml

@@ -17,32 +17,32 @@ providers:
   - provider_id: ${env.CEREBRAS_API_KEY:+cerebras}
     provider_type: remote::cerebras
     config:
-      base_url: https://api.cerebras.ai
+      base_url: https://api.cerebras.ai/v1
       api_key: ${env.CEREBRAS_API_KEY:=}
   - provider_id: ${env.OLLAMA_URL:+ollama}
     provider_type: remote::ollama
     config:
-      url: ${env.OLLAMA_URL:=http://localhost:11434}
+      base_url: ${env.OLLAMA_URL:=http://localhost:11434/v1}
   - provider_id: ${env.VLLM_URL:+vllm}
     provider_type: remote::vllm
     config:
-      url: ${env.VLLM_URL:=}
+      base_url: ${env.VLLM_URL:=}
       max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
       api_token: ${env.VLLM_API_TOKEN:=fake}
       tls_verify: ${env.VLLM_TLS_VERIFY:=true}
   - provider_id: ${env.TGI_URL:+tgi}
     provider_type: remote::tgi
     config:
-      url: ${env.TGI_URL:=}
+      base_url: ${env.TGI_URL:=}
   - provider_id: fireworks
     provider_type: remote::fireworks
     config:
-      url: https://api.fireworks.ai/inference/v1
+      base_url: https://api.fireworks.ai/inference/v1
       api_key: ${env.FIREWORKS_API_KEY:=}
   - provider_id: together
     provider_type: remote::together
     config:
-      url: https://api.together.xyz/v1
+      base_url: https://api.together.xyz/v1
       api_key: ${env.TOGETHER_API_KEY:=}
   - provider_id: bedrock
     provider_type: remote::bedrock
@@ -52,9 +52,8 @@ providers:
   - provider_id: ${env.NVIDIA_API_KEY:+nvidia}
     provider_type: remote::nvidia
     config:
-      url: ${env.NVIDIA_BASE_URL:=https://integrate.api.nvidia.com}
+      base_url: ${env.NVIDIA_BASE_URL:=https://integrate.api.nvidia.com/v1}
       api_key: ${env.NVIDIA_API_KEY:=}
-      append_api_version: ${env.NVIDIA_APPEND_API_VERSION:=True}
   - provider_id: openai
     provider_type: remote::openai
     config:
@@ -76,18 +75,18 @@ providers:
   - provider_id: groq
     provider_type: remote::groq
     config:
-      url: https://api.groq.com
+      base_url: https://api.groq.com/openai/v1
       api_key: ${env.GROQ_API_KEY:=}
   - provider_id: sambanova
     provider_type: remote::sambanova
     config:
-      url: https://api.sambanova.ai/v1
+      base_url: https://api.sambanova.ai/v1
       api_key: ${env.SAMBANOVA_API_KEY:=}
   - provider_id: ${env.AZURE_API_KEY:+azure}
     provider_type: remote::azure
     config:
       api_key: ${env.AZURE_API_KEY:=}
-      api_base: ${env.AZURE_API_BASE:=}
+      base_url: ${env.AZURE_API_BASE:=}
       api_version: ${env.AZURE_API_VERSION:=}
       api_type: ${env.AZURE_API_TYPE:=}
   - provider_id: sentence-transformers