feat: add gRPC handler with event validation and publishing

Handler implementation:
- EventStore interface (consumer-side)
- Server with PublishEvent, QueryEvents, CountEvents, PublishBatch
- pb.Event <-> nostr.Event conversion helpers
- Signature and ID validation using existing nostr package
- Canonical JSON generation for storage

9 tests passing

1 files changed, 40 insertions, 0 deletions

diff --git a/internal/handler/grpc/convert.go b/internal/handler/grpc/convert.go
new file mode 100644
index 0000000..19505cd
--- /dev/null
+++ b/internal/handler/grpc/convert.go
@@ -0,0 +1,40 @@
+package grpc
+
+import (
+        pb "northwest.io/nostr-grpc/api/nostr/v1"
+        "northwest.io/nostr-grpc/internal/nostr"
+)
+
+func NostrToPB(n *nostr.Event) *pb.Event {
+        tags := make([]*pb.Tag, len(n.Tags))
+        for i, tag := range n.Tags {
+                tags[i] = &pb.Tag{Values: tag}
+        }
+
+        return &pb.Event{
+                Id:        n.ID,
+                Pubkey:    n.PubKey,
+                CreatedAt: n.CreatedAt,
+                Kind:      int32(n.Kind),
+                Tags:      tags,
+                Content:   n.Content,
+                Sig:       n.Sig,
+        }
+}
+
+func PBToNostr(e *pb.Event) *nostr.Event {
+        tags := make(nostr.Tags, len(e.Tags))
+        for i, tag := range e.Tags {
+                tags[i] = tag.Values
+        }
+
+        return &nostr.Event{
+                ID:        e.Id,
+                PubKey:    e.Pubkey,
+                CreatedAt: e.CreatedAt,
+                Kind:      int(e.Kind),
+                Tags:      tags,
+                Content:   e.Content,
+                Sig:       e.Sig,
+        }
+}