Add Kimi (Moonshot AI) provider support

- OAuth2 device authorization grant flow (RFC 8628) for authentication
- Streaming and non-streaming chat completions via OpenAI-compatible API
- Models: kimi-k2, kimi-k2-thinking, kimi-k2.5
- CLI `--kimi-login` command for device flow auth
- Token management with automatic refresh
- Thinking/reasoning effort support for thinking-enabled models

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/server/main.go

@@ -63,6 +63,7 @@ func main() {
 	var noBrowser bool
 	var oauthCallbackPort int
 	var antigravityLogin bool
+	var kimiLogin bool
 	var projectID string
 	var vertexImport string
 	var configPath string
@@ -78,6 +79,7 @@ func main() {
 	flag.BoolVar(&noBrowser, "no-browser", false, "Don't open browser automatically for OAuth")
 	flag.IntVar(&oauthCallbackPort, "oauth-callback-port", 0, "Override OAuth callback port (defaults to provider-specific port)")
 	flag.BoolVar(&antigravityLogin, "antigravity-login", false, "Login to Antigravity using OAuth")
+	flag.BoolVar(&kimiLogin, "kimi-login", false, "Login to Kimi using OAuth")
 	flag.StringVar(&projectID, "project_id", "", "Project ID (Gemini only, not required)")
 	flag.StringVar(&configPath, "config", DefaultConfigPath, "Configure File Path")
 	flag.StringVar(&vertexImport, "vertex-import", "", "Import Vertex service account key JSON file")
@@ -468,6 +470,8 @@ func main() {
 		cmd.DoIFlowLogin(cfg, options)
 	} else if iflowCookie {
 		cmd.DoIFlowCookieAuth(cfg, options)
+	} else if kimiLogin {
+		cmd.DoKimiLogin(cfg, options)
 	} else {
 		// In cloud deploy mode without config file, just wait for shutdown signals
 		if isCloudDeploy && !configFileExists {