feat(auth, docs): add SDK guides and local password support for management

- Added extensive SDK usage guides for `cliproxy`, `sdk/access`, and watcher integration.
- Introduced `--password` flag for specifying local management access passwords.
- Enhanced management API with local password checks to secure localhost requests.
- Updated documentation to reflect the new password functionality.

docs/sdk-usage.md

@@ -0,0 +1,163 @@
+# CLI Proxy SDK Guide
+
+The `sdk/cliproxy` module exposes the proxy as a reusable Go library so external programs can embed the routing, authentication, hot‑reload, and translation layers without depending on the CLI binary.
+
+## Install & Import
+
+```bash
+go get github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy
+```
+
+```go
+import (
+    "context"
+    "errors"
+    "time"
+
+    "github.com/router-for-me/CLIProxyAPI/v6/internal/config"
+    "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy"
+)
+```
+
+Note the `/v6` module path.
+
+## Minimal Embed
+
+```go
+cfg, err := config.LoadConfig("config.yaml")
+if err != nil { panic(err) }
+
+svc, err := cliproxy.NewBuilder().
+    WithConfig(cfg).
+    WithConfigPath("config.yaml"). // absolute or working-dir relative
+    Build()
+if err != nil { panic(err) }
+
+ctx, cancel := context.WithCancel(context.Background())
+defer cancel()
+
+if err := svc.Run(ctx); err != nil && !errors.Is(err, context.Canceled) {
+    panic(err)
+}
+```
+
+The service manages config/auth watching, background token refresh, and graceful shutdown. Cancel the context to stop it.
+
+## Server Options (middleware, routes, logs)
+
+The server accepts options via `WithServerOptions`:
+
+```go
+svc, _ := cliproxy.NewBuilder().
+  WithConfig(cfg).
+  WithConfigPath("config.yaml").
+  WithServerOptions(
+    // Add global middleware
+    cliproxy.WithMiddleware(func(c *gin.Context) { c.Header("X-Embed", "1"); c.Next() }),
+    // Tweak gin engine early (CORS, trusted proxies, etc.)
+    cliproxy.WithEngineConfigurator(func(e *gin.Engine) { e.ForwardedByClientIP = true }),
+    // Add your own routes after defaults
+    cliproxy.WithRouterConfigurator(func(e *gin.Engine, _ *handlers.BaseAPIHandler, _ *config.Config) {
+      e.GET("/healthz", func(c *gin.Context) { c.String(200, "ok") })
+    }),
+    // Override request log writer/dir
+    cliproxy.WithRequestLoggerFactory(func(cfg *config.Config, cfgPath string) logging.RequestLogger {
+      return logging.NewFileRequestLogger(true, "logs", filepath.Dir(cfgPath))
+    }),
+  ).
+  Build()
+```
+
+These options mirror the internals used by the CLI server.
+
+## Management API (when embedded)
+
+- Management endpoints are mounted only when `remote-management.secret-key` is set in `config.yaml`.
+- Remote access additionally requires `remote-management.allow-remote: true`.
+- See MANAGEMENT_API.md for endpoints. Your embedded server exposes them under `/v0/management` on the configured port.
+
+## Using the Core Auth Manager
+
+The service uses a core `auth.Manager` for selection, execution, and auto‑refresh. When embedding, you can provide your own manager to customize transports or hooks:
+
+```go
+core := coreauth.NewManager(coreauth.NewFileStore(cfg.AuthDir), nil, nil)
+core.SetRoundTripperProvider(myRTProvider) // per‑auth *http.Transport
+
+svc, _ := cliproxy.NewBuilder().
+    WithConfig(cfg).
+    WithConfigPath("config.yaml").
+    WithCoreAuthManager(core).
+    Build()
+```
+
+Implement a custom per‑auth transport:
+
+```go
+type myRTProvider struct{}
+func (myRTProvider) RoundTripperFor(a *coreauth.Auth) http.RoundTripper {
+    if a == nil || a.ProxyURL == "" { return nil }
+    u, _ := url.Parse(a.ProxyURL)
+    return &http.Transport{ Proxy: http.ProxyURL(u) }
+}
+```
+
+Programmatic execution is available on the manager:
+
+```go
+// Non‑streaming
+resp, err := core.Execute(ctx, []string{"gemini"}, req, opts)
+
+// Streaming
+chunks, err := core.ExecuteStream(ctx, []string{"gemini"}, req, opts)
+for ch := range chunks { /* ... */ }
+```
+
+Note: Built‑in provider executors are wired automatically when you run the `Service`. If you want to use `Manager` stand‑alone without the HTTP server, you must register your own executors that implement `auth.ProviderExecutor`.
+
+## Custom Client Sources
+
+Replace the default loaders if your creds live outside the local filesystem:
+
+```go
+type memoryTokenProvider struct{}
+func (p *memoryTokenProvider) Load(ctx context.Context, cfg *config.Config) (*cliproxy.TokenClientResult, error) {
+    // Populate from memory/remote store and return counts
+    return &cliproxy.TokenClientResult{}, nil
+}
+
+svc, _ := cliproxy.NewBuilder().
+  WithConfig(cfg).
+  WithConfigPath("config.yaml").
+  WithTokenClientProvider(&memoryTokenProvider{}).
+  WithAPIKeyClientProvider(cliproxy.NewAPIKeyClientProvider()).
+  Build()
+```
+
+## Hooks
+
+Observe lifecycle without patching internals:
+
+```go
+hooks := cliproxy.Hooks{
+  OnBeforeStart: func(cfg *config.Config) { log.Infof("starting on :%d", cfg.Port) },
+  OnAfterStart:  func(s *cliproxy.Service) { log.Info("ready") },
+}
+svc, _ := cliproxy.NewBuilder().WithConfig(cfg).WithConfigPath("config.yaml").WithHooks(hooks).Build()
+```
+
+## Shutdown
+
+`Run` defers `Shutdown`, so cancelling the parent context is enough. To stop manually:
+
+```go
+ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+defer cancel()
+_ = svc.Shutdown(ctx)
+```
+
+## Notes
+
+- Hot reload: changes to `config.yaml` and `auths/` are picked up automatically.
+- Request logging can be toggled at runtime via the Management API.
+- Gemini Web features (`gemini-web.*`) are honored in the embedded server.