feat: phase 2 relay implementation

Implement the Axon relay as relay/ (module axon/relay). Includes:
- WebSocket framing (RFC 6455, no external deps) in relay/websocket/
- Per-connection auth: challenge/response with ed25519 + allowlist check
- Ingest pipeline: sig verify, dedup, ephemeral fanout, SQLite persistence
- Subscription manager with prefix-matching filter fanout in relay/subscription/
- SQLite storage with WAL/cache config and UNION query builder in relay/storage/
- Graceful shutdown on SIGINT/SIGTERM
- Filter/TagFilter types added to axon core package (required by relay)

1 files changed, 30 insertions, 0 deletions

diff --git a/relay/go.mod b/relay/go.mod
new file mode 100644
index 0000000..a3d424a
--- /dev/null
+++ b/relay/go.mod
@@ -0,0 +1,30 @@
+module axon/relay
+
+go 1.25.5
+
+require (
+        axon v0.0.0
+        github.com/vmihailenco/msgpack/v5 v5.4.1
+        gopkg.in/yaml.v3 v3.0.1
+        modernc.org/sqlite v1.33.1
+)
+
+require (
+        github.com/dustin/go-humanize v1.0.1 // indirect
+        github.com/google/uuid v1.6.0 // indirect
+        github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
+        github.com/mattn/go-isatty v0.0.20 // indirect
+        github.com/ncruces/go-strftime v0.1.9 // indirect
+        github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+        github.com/vmihailenco/tagparser/v2 v2.0.0 // indirect
+        golang.org/x/crypto v0.48.0 // indirect
+        golang.org/x/sys v0.41.0 // indirect
+        modernc.org/gc/v3 v3.0.0-20240107210532-573471604cb6 // indirect
+        modernc.org/libc v1.55.3 // indirect
+        modernc.org/mathutil v1.6.0 // indirect
+        modernc.org/memory v1.8.0 // indirect
+        modernc.org/strutil v1.2.0 // indirect
+        modernc.org/token v1.1.0 // indirect
+)
+
+replace axon => ../