fix(cordis): fail-closed auth guards for user/message_gateway/admin (#1)

* autoresearch iter 23: fail-closed auth guarding for user/message_gateway

Both plugins resolve contracts.AuthService in Apply to build their route
middleware, but declared only DBService in Inject(). The kernel gates a
plugin's Apply solely on declared deps, and cmd/app.go registers user
before auth, so user mounted first, core.Inject failed, and loginMW
silently degraded to a pass-through closure — leaving /api/v1/user
change-password, profile and access-tokens unguarded. message_gateway
was saved only by its later list position.

Declare AuthService in Inject() for both, and pin the property with a
reconcile-level test that mirrors production registration order and
asserts the real auth middleware reaches the route table.

* autoresearch iter 24: make auth middleware fallbacks fail closed

user, message_gateway and admin each fell back to a c.Next() closure when
contracts.AuthService could not be resolved, so a route would be served as
if authenticated. For admin this is reachable at runtime: OnDispose calls
service.ResetServices(), which nils the global the per-request guard reads,
so requests still in flight during dispose bypass authorization entirely.

Add ginutil.AuthUnavailable() and bind every fallback to it, with a test
that drives each plugin's registered guard without an auth service present
and asserts the request is aborted rather than passed through.

* chore(autoresearch): log iter 23 (fail-open auth ordering, proven)

* autoresearch iter 24 follow-up: let staticcheck infer the auth guard type

* docs(autoresearch): log iters 24-25 and lessons 9-11 (declared-dep bug class, gate discipline)

backend/plugins/domain/admin/plugin.go

@@ -8,6 +8,7 @@ import (
 	"Wavelet/core"
 	"Wavelet/core/contracts"
 	"Wavelet/core/extpoints"
+	"Wavelet/pkg/ginutil"
 	"Wavelet/plugins/domain/admin/handler"
 	"Wavelet/plugins/domain/admin/model"
 	"Wavelet/plugins/domain/admin/service"
@@ -142,6 +143,7 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 	})
 
 	// 0a. Dynamic Auth Middlewares
+	denyAuth := ginutil.AuthUnavailable()
 	var loginMW gin.HandlerFunc = func(c *gin.Context) {
 		if authSvc := service.GetAuthService(c.Request.Context()); authSvc != nil {
 			if mw, ok := authSvc.RequireAuthMiddleware().(gin.HandlerFunc); ok {
@@ -149,7 +151,7 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 				return
 			}
 		}
-		c.Next()
+		denyAuth(c)
 	}
 	var adminMW gin.HandlerFunc = func(c *gin.Context) {
 		if authSvc := service.GetAuthService(c.Request.Context()); authSvc != nil {
@@ -158,7 +160,7 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 				return
 			}
 		}
-		c.Next()
+		denyAuth(c)
 	}
 
 	// 0b. Register migrations