feat: add Together AI integration and provider implementation guide

- Create detailed provider implementation guide with:
  - Architecture overview and implementation steps
  - Configuration patterns and best practices
  - Testing checklist and Docker integration guide
  - Example using Together AI implementation
- Add Together AI as new provider with:
  - Environment variables and Docker configuration
  - Support for Qwen, Llama, and Mixtral models
  - API key and base URL management
  - OpenAI-compatible API integration

Dockerfile

@@ -25,6 +25,8 @@ ARG ANTHROPIC_API_KEY
 ARG OPEN_ROUTER_API_KEY
 ARG GOOGLE_GENERATIVE_AI_API_KEY
 ARG OLLAMA_API_BASE_URL
+ARG TOGETHER_API_KEY
+ARG TOGETHER_API_BASE_URL
 ARG VITE_LOG_LEVEL=debug
 ARG DEFAULT_NUM_CTX
 
@@ -36,6 +38,8 @@ ENV WRANGLER_SEND_METRICS=false \
     OPEN_ROUTER_API_KEY=${OPEN_ROUTER_API_KEY} \
     GOOGLE_GENERATIVE_AI_API_KEY=${GOOGLE_GENERATIVE_AI_API_KEY} \
     OLLAMA_API_BASE_URL=${OLLAMA_API_BASE_URL} \
+    TOGETHER_API_KEY=${TOGETHER_API_KEY} \
+    TOGETHER_API_BASE_URL=${TOGETHER_API_BASE_URL} \
     VITE_LOG_LEVEL=${VITE_LOG_LEVEL} \
     DEFAULT_NUM_CTX=${DEFAULT_NUM_CTX}
 
@@ -58,6 +62,8 @@ ARG ANTHROPIC_API_KEY
 ARG OPEN_ROUTER_API_KEY
 ARG GOOGLE_GENERATIVE_AI_API_KEY
 ARG OLLAMA_API_BASE_URL
+ARG TOGETHER_API_KEY
+ARG TOGETHER_API_BASE_URL
 ARG VITE_LOG_LEVEL=debug
 ARG DEFAULT_NUM_CTX
 
@@ -68,6 +74,8 @@ ENV GROQ_API_KEY=${GROQ_API_KEY} \
     OPEN_ROUTER_API_KEY=${OPEN_ROUTER_API_KEY} \
     GOOGLE_GENERATIVE_AI_API_KEY=${GOOGLE_GENERATIVE_AI_API_KEY} \
     OLLAMA_API_BASE_URL=${OLLAMA_API_BASE_URL} \
+    TOGETHER_API_KEY=${TOGETHER_API_KEY} \
+    TOGETHER_API_BASE_URL=${TOGETHER_API_BASE_URL} \
     VITE_LOG_LEVEL=${VITE_LOG_LEVEL} \
     DEFAULT_NUM_CTX=${DEFAULT_NUM_CTX}