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/validation/timestamp.go

@@ -0,0 +1,17 @@
+package validation
+
+import (
+	"time"
+
+	"git.mleku.dev/mleku/nostr/encoders/event"
+)
+
+// ValidateTimestamp checks that the event timestamp is not too far in the future.
+// maxFutureSeconds is the maximum allowed seconds ahead of current time.
+func ValidateTimestamp(ev *event.E, maxFutureSeconds int64) Result {
+	now := time.Now().Unix()
+	if ev.CreatedAt > now+maxFutureSeconds {
+		return Invalid("timestamp too far in the future")
+	}
+	return OK()
+}