Decompose handle-event.go into DDD domain services (v0.36.15)

Major refactoring of event handling into clean, testable domain services:

- Add pkg/event/validation: JSON hex validation, signature verification,
  timestamp bounds, NIP-70 protected tag validation
- Add pkg/event/authorization: Policy and ACL authorization decisions,
  auth challenge handling, access level determination
- Add pkg/event/routing: Event router registry with ephemeral and delete
  handlers, kind-based dispatch
- Add pkg/event/processing: Event persistence, delivery to subscribers,
  and post-save hooks (ACL reconfig, sync, relay groups)
- Reduce handle-event.go from 783 to 296 lines (62% reduction)
- Add comprehensive unit tests for all new domain services
- Refactor database tests to use shared TestMain setup
- Fix blossom URL test expectations (missing "/" separator)
- Add go-memory-optimization skill and analysis documentation
- Update DDD_ANALYSIS.md to reflect completed decomposition

Files modified:
- app/handle-event.go: Slim orchestrator using domain services
- app/server.go: Service initialization and interface wrappers
- app/handle-event-types.go: Shared types (OkHelper, result types)
- pkg/event/validation/*: New validation service package
- pkg/event/authorization/*: New authorization service package
- pkg/event/routing/*: New routing service package
- pkg/event/processing/*: New processing service package
- pkg/database/*_test.go: Refactored to shared TestMain
- pkg/blossom/http_test.go: Fixed URL format expectations

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/event/routing/ephemeral.go

@@ -0,0 +1,30 @@
+package routing
+
+import (
+	"git.mleku.dev/mleku/nostr/encoders/event"
+	"git.mleku.dev/mleku/nostr/encoders/kind"
+)
+
+// Publisher abstracts event delivery to subscribers.
+type Publisher interface {
+	// Deliver sends an event to all matching subscribers.
+	Deliver(ev *event.E)
+}
+
+// IsEphemeral checks if a kind is ephemeral (20000-29999).
+func IsEphemeral(k uint16) bool {
+	return kind.IsEphemeral(k)
+}
+
+// MakeEphemeralHandler creates a handler for ephemeral events.
+// Ephemeral events (kinds 20000-29999):
+// - Are NOT persisted to the database
+// - Are immediately delivered to subscribers
+func MakeEphemeralHandler(publisher Publisher) Handler {
+	return func(ev *event.E, authedPubkey []byte) Result {
+		// Clone and deliver immediately without persistence
+		cloned := ev.Clone()
+		go publisher.Deliver(cloned)
+		return HandledResult("")
+	}
+}