Add spider functionality for relay crawling, marker management, and new SpiderMode config.

- Introduced the `spider` package for relay crawling, including periodic tasks and one-time sync capabilities.
- Added `SetMarker`, `GetMarker`, `HasMarker`, and `DeleteMarker` methods in the database for marker management.
- Updated configuration with `SpiderMode` and `SpiderFrequency` options to enable and customize spider behavior.
- Integrated `spider` initialization into the main application flow.
- Improved tag handling, NIP-70 compliance, and protected tag validation in event processing.
- Removed unnecessary logging and replaced `errorf` with `fmt.Errorf` for better error handling.
- Incremented version to `v0.5.0`.

pkg/acl/follows.go

@@ -360,6 +360,16 @@ func (f *Follows) Syncer() {
 	f.updated <- struct{}{}
 }
 
+// GetFollowedPubkeys returns a copy of the followed pubkeys list
+func (f *Follows) GetFollowedPubkeys() [][]byte {
+	f.followsMx.RLock()
+	defer f.followsMx.RUnlock()
+	
+	followedPubkeys := make([][]byte, len(f.follows))
+	copy(followedPubkeys, f.follows)
+	return followedPubkeys
+}
+
 func init() {
 	log.T.F("registering follows ACL")
 	Registry.Register(new(Follows))