feat(auth): implement decoupled sliding-window rate limiting for login and oauth

backend/plugins/infra/cache_memory/plugin.go

@@ -7,6 +7,7 @@ package cache_memory
 import (
 	"Wavelet/core"
 	"Wavelet/core/contracts"
+	"Wavelet/pkg/limiter"
 )
 
 const defaultRAMCapacity = 10000
@@ -79,5 +80,6 @@ func (p *Plugin) Apply(ctx *core.Context) error {
 	}
 
 	core.Provide[contracts.CacheService](ctx, svc)
+	core.Provide[contracts.LimiterService](ctx, limiter.NewMemoryLimiter())
 	return nil
 }

backend/plugins/infra/cache_memory/plugin_test.go

@@ -78,4 +78,14 @@ func TestCacheMemoryPlugin(t *testing.T) {
 	var tempVal string
 	err = cacheSvc.Get(reqCtx, "temp_key", &tempVal)
 	assert.ErrorIs(t, err, contracts.ErrCacheMiss)
+
+	// 6. LimiterService
+	limiterSvc, err := core.Inject[contracts.LimiterService](ctx)
+	require.NoError(t, err)
+	require.NotNil(t, limiterSvc)
+
+	rateRes, err := limiterSvc.Allow(reqCtx, "key_a", contracts.Rate{Limit: 2, Period: time.Minute})
+	require.NoError(t, err)
+	assert.True(t, rateRes.Allowed)
+	assert.Equal(t, 1, rateRes.Remaining)
 }