fix: raise provider HTTP timeouts from 30s to 10min

30-second resty client timeout was killing long streaming responses
mid-generation. Models with large output windows (e.g. deepseek-v4-pro
at 384K max_tokens) routinely exceed 30s. Raised all providers to
10 minutes (Ollama already at 15min, unchanged). Circuit breaker
recovery timeout raised from 30s to 5min.

internal/providers/openai.go

@@ -20,7 +20,7 @@ type OpenAIProvider struct {
 
 func NewOpenAIProvider(cfg config.OpenAIConfig, apiKey string) *OpenAIProvider {
 	return &OpenAIProvider{
-		client: resty.New().SetTimeout(30 * time.Second),
+		client: resty.New().SetTimeout(10 * time.Minute),
 		config: cfg,
 		apiKey: apiKey,
 	}