feat(auth): add PAT auth, scoped REST/MCP access, CSRF, and tenant isolation

Introduce Personal Access Tokens (nzp_*) as a stateless auth path alongside
JWT, gated per-endpoint by a scope middleware (nezha:{resource}:{verb}) with
fail-closed empty-scope defaults and a server-id whitelist. Self-management
endpoints (profile, api-tokens, oauth2 bind, refresh-token) explicitly reject
PATs to block privilege-escalation chains. A revoke registry tears down active
long-lived connections (terminal, fm, ws, transfer, mcp) the moment a PAT is
deleted, with a tombstone closing the revoke->register race.

Add an MCP endpoint that proxies tool calls (exec, fs read/write/delete,
transfer) to agents over gRPC, guarded by origin/DNS-rebinding checks, a
per-token rate limiter, audit logging, and a kill switch. Serialize all
sends through the IOStream wrapper to honour grpc-go's concurrency contract.

Add CSRF double-submit protection on unsafe cookie-authenticated methods,
exempting authenticated PAT requests by context identity (not a forgeable
Authorization header). Apply visibility/whitelist filtering consistently
across list, get-by-id, and mutate paths to enforce tenant isolation.

Migrate legacy mcp:* scopes: rewrite read/exec to nezha:* equivalents and
drop dangerous write/delete/wildcard grants.

Co-authored-by: cloudcode <cloudcode@users.noreply.github.com>

cmd/dashboard/controller/mcp_transfer_path_cap_test.go

@@ -0,0 +1,38 @@
+package controller
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/nezhahq/nezha/model"
+	"github.com/nezhahq/nezha/service/singleton"
+)
+
+func TestValidateTransferPathRejectsOversizedPath(t *testing.T) {
+	if err := validateTransferPath(strings.Repeat("a", maxTransferPathLen+1)); err == nil {
+		t.Fatal("path longer than maxTransferPathLen must be rejected to bound transferEntry memory")
+	}
+	if err := validateTransferPath(""); err == nil {
+		t.Fatal("empty path must be rejected")
+	}
+	if err := validateTransferPath("/etc/hostname"); err != nil {
+		t.Fatalf("a normal path must be accepted, got %v", err)
+	}
+}
+
+// openFsTransferStream must refuse to start a new transfer (and never reach
+// SendTask) once the administrator has disabled MCP, closing the race window
+// between revalidateTransferEntry and stream creation.
+func TestOpenFsTransferStreamRefusesWhenMCPDisabled(t *testing.T) {
+	originalConf := singleton.Conf
+	t.Cleanup(func() { singleton.Conf = originalConf })
+	cfg := &model.Config{}
+	cfg.SetMCPEnabled(false)
+	singleton.Conf = &singleton.ConfigClass{Config: cfg}
+
+	_, _, err := openFsTransferStream(context.Background(), 1, &model.FsTransferRequest{})
+	if err == nil {
+		t.Fatal("transfer stream must not open while MCP is disabled")
+	}
+}