perf(upload): optimize file hot paths and incremental admin stats

- Use RWMutex for disk cache reads and singleflight for WebP cache misses
- Cache migration read-only state and file access whitelist with pub/sub invalidation
- Add w_upload_stats incremental counters updated on upload/delete
- Add w_uploads composite indexes and goose backfill migrations
- Document performance analysis in docs/PERFORMANCE.md
- Fix RegisterCustomRoutes to accept apiV1Router parameter

internal/apps/upload/access_cache.go

@@ -0,0 +1,200 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package upload
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Rain-kl/Wavelet/internal/db"
+	"github.com/Rain-kl/Wavelet/internal/model"
+	"github.com/Rain-kl/Wavelet/internal/storage"
+)
+
+const accessCacheTTL = 5 * time.Second
+
+const fileAccessInvalidationChannel = "upload:file_access_invalidation"
+
+type migrationAccessState struct {
+	readOnly  bool
+	target    storage.Config
+	hasTarget bool
+	targetErr error
+	loadErr   error
+}
+
+var (
+	accessCacheOnce sync.Once
+
+	migrationAccessMu       sync.RWMutex
+	migrationAccessCached   migrationAccessState
+	migrationAccessValid    bool
+	migrationAccessCheckedAt time.Time
+
+	fileAccessWhitelistMu      sync.RWMutex
+	fileAccessWhitelistTypes     map[string]struct{}
+	fileAccessWhitelistValid     bool
+	fileAccessWhitelistCheckedAt time.Time
+)
+
+// ResetAccessCaches clears in-process upload access caches.
+func ResetAccessCaches() {
+	migrationAccessMu.Lock()
+	migrationAccessValid = false
+	migrationAccessMu.Unlock()
+
+	fileAccessWhitelistMu.Lock()
+	fileAccessWhitelistValid = false
+	fileAccessWhitelistTypes = nil
+	fileAccessWhitelistMu.Unlock()
+}
+
+// PublishAccessCacheInvalidation broadcasts upload access cache eviction to all nodes.
+func PublishAccessCacheInvalidation(ctx context.Context) {
+	if db.Redis != nil {
+		_ = db.Redis.Publish(ctx, fileAccessInvalidationChannel, "reset").Err()
+	}
+}
+
+func ensureAccessCacheListener() {
+	accessCacheOnce.Do(startAccessCacheInvalidationListener)
+}
+
+func startAccessCacheInvalidationListener() {
+	if db.Redis == nil {
+		return
+	}
+
+	go func() {
+		pubsub := db.Redis.Subscribe(
+			context.Background(),
+			storage.ConfigInvalidationChannel,
+			fileAccessInvalidationChannel,
+		)
+		defer func() {
+			_ = pubsub.Close()
+		}()
+
+		for range pubsub.Channel() {
+			ResetAccessCaches()
+		}
+	}()
+}
+
+func loadMigrationAccessState(ctx context.Context) migrationAccessState {
+	ensureAccessCacheListener()
+
+	migrationAccessMu.RLock()
+	if migrationAccessValid && time.Since(migrationAccessCheckedAt) < accessCacheTTL {
+		state := migrationAccessCached
+		migrationAccessMu.RUnlock()
+		return state
+	}
+	migrationAccessMu.RUnlock()
+
+	migrationAccessMu.Lock()
+	defer migrationAccessMu.Unlock()
+
+	if migrationAccessValid && time.Since(migrationAccessCheckedAt) < accessCacheTTL {
+		return migrationAccessCached
+	}
+
+	migrationAccessCached = buildMigrationAccessState(ctx)
+	migrationAccessValid = true
+	migrationAccessCheckedAt = time.Now()
+	return migrationAccessCached
+}
+
+func buildMigrationAccessState(ctx context.Context) migrationAccessState {
+	execution, ok, err := latestStorageMigrationExecution(ctx)
+	if err != nil {
+		return migrationAccessState{loadErr: err, readOnly: true}
+	}
+	if !ok {
+		return migrationAccessState{}
+	}
+
+	state := migrationAccessState{
+		readOnly: execution.Status != model.TaskExecutionStatusSucceeded,
+	}
+	if execution.Status == model.TaskExecutionStatusSucceeded {
+		return state
+	}
+
+	target, err := parseMigrationTargetConfig(ctx, []byte(execution.Payload))
+	if err != nil {
+		state.targetErr = err
+		return state
+	}
+
+	state.target = target
+	state.hasTarget = true
+	return state
+}
+
+func loadFileAccessWhitelist(ctx context.Context) map[string]struct{} {
+	ensureAccessCacheListener()
+
+	fileAccessWhitelistMu.RLock()
+	if fileAccessWhitelistValid && time.Since(fileAccessWhitelistCheckedAt) < accessCacheTTL {
+		types := fileAccessWhitelistTypes
+		fileAccessWhitelistMu.RUnlock()
+		return types
+	}
+	fileAccessWhitelistMu.RUnlock()
+
+	fileAccessWhitelistMu.Lock()
+	defer fileAccessWhitelistMu.Unlock()
+
+	if fileAccessWhitelistValid && time.Since(fileAccessWhitelistCheckedAt) < accessCacheTTL {
+		return fileAccessWhitelistTypes
+	}
+
+	fileAccessWhitelistTypes = fetchFileAccessWhitelist(ctx)
+	fileAccessWhitelistValid = true
+	fileAccessWhitelistCheckedAt = time.Now()
+	return fileAccessWhitelistTypes
+}
+
+func fetchFileAccessWhitelist(ctx context.Context) map[string]struct{} {
+	whitelist := parseFileAccessWhitelist(ctx)
+	types := make(map[string]struct{}, len(whitelist))
+	for _, item := range whitelist {
+		types[strings.ToLower(item)] = struct{}{}
+	}
+	return types
+}
+
+func parseFileAccessWhitelist(ctx context.Context) []string {
+	var sc model.SystemConfig
+	if err := sc.GetByKey(ctx, model.ConfigKeyFileAccessWhitelist); err != nil || sc.Value == "" {
+		return []string{defaultPublicUploadType}
+	}
+
+	var whitelist []string
+	if err := json.Unmarshal([]byte(sc.Value), &whitelist); err == nil && len(whitelist) > 0 {
+		return whitelist
+	}
+
+	whitelist = parseCommaSeparatedWhitelist(sc.Value)
+	if len(whitelist) == 0 {
+		return []string{defaultPublicUploadType}
+	}
+	return whitelist
+}
+
+func parseCommaSeparatedWhitelist(value string) []string {
+	parts := strings.Split(value, ",")
+	whitelist := make([]string, 0, len(parts))
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part != "" {
+			whitelist = append(whitelist, part)
+		}
+	}
+	return whitelist
+}