feat(vault-tui): implement KV client and service for managing secrets

- Added internal/vault/client.go for creating a Vault client with configuration settings.
- Introduced internal/vault/errors.go to classify Vault API errors for better UI handling.
- Created internal/vault/kv.go to manage KV secrets, including listing, reading, writing, and deleting operations.
- Implemented internal/vault/mounts.go to list and describe secret engine mounts.
- Developed internal/vault/service.go to provide a unified entry point for Vault operations.
- Added internal/vault/kv_test.go for comprehensive testing of KV operations.
- Introduced internal/ui/toast.go for transient notifications in the UI.
- Added renovate.json for dependency management and updates.

internal/cli/oidc.go

@@ -0,0 +1,47 @@
+package cli
+
+import (
+	"git.morlana.online/f.weber/vault-tui/internal/auth"
+	"git.morlana.online/f.weber/vault-tui/internal/auth/oidc"
+)
+
+// init registers a default-configured OIDC method so it appears in
+// auth.Default() for listing/help purposes. app.Method special-cases
+// "oidc" to build a fresh oidc.Method from the profile's actual settings
+// (see oidcMethod below) instead of using this registered instance, because
+// OIDC's port/callback/timeout are meaningfully per-profile.
+func init() {
+	auth.Register(oidc.Method{})
+}
+
+func (a *App) oidcMethod() auth.Method {
+	o := a.Settings.Auth.OIDC
+	cfg := oidc.Config{
+		Mount:          a.Settings.Auth.Mount,
+		Role:           a.Settings.Auth.Params["role"],
+		ListenAddress:  o.ListenAddress,
+		CallbackMethod: o.CallbackMethod,
+		CallbackHost:   o.CallbackHost,
+		CallbackPath:   o.CallbackPath,
+		BrowserCommand: a.Settings.BrowserCommand,
+	}
+	if o.Port != nil {
+		cfg.Port = *o.Port
+	}
+	if o.CallbackPort != nil {
+		cfg.CallbackPort = *o.CallbackPort
+	}
+	if o.SkipBrowser != nil {
+		cfg.SkipBrowser = *o.SkipBrowser
+	}
+	if o.AbortOnBrowserError != nil {
+		cfg.AbortOnBrowserError = *o.AbortOnBrowserError
+	}
+	if o.Timeout != nil {
+		cfg.Timeout = *o.Timeout
+	}
+	if cfg.Mount == "" {
+		cfg.Mount = "oidc"
+	}
+	return oidc.Method{Cfg: cfg}
+}