refactor: federation uses persistent WS instead of HTTP polling

- Server-to-server communication via WebSocket at /v1/federation/ws
- Auth as first WS frame (shared secret), presence + forwards over same connection
- Auto-reconnect every 3s on disconnect, instant presence push on connect
- Replaces HTTP REST polling (no more 5s intervals, lower latency)
- Removed dead HMAC helpers (auth is now direct secret comparison over WS)
- Simplified ARCHITECTURE.md mermaid diagrams for Gitea rendering

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/Cargo.lock

@@ -163,7 +163,7 @@ dependencies = [
  "sha1",
  "sync_wrapper",
  "tokio",
- "tokio-tungstenite",
+ "tokio-tungstenite 0.24.0",
  "tower 0.5.3",
  "tower-layer",
  "tower-service",
@@ -1795,7 +1795,7 @@ dependencies = [
  "once_cell",
  "socket2",
  "tracing",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -2593,6 +2593,20 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "tokio-tungstenite"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c83b561d025642014097b66e6c1bb422783339e0909e4429cde4749d1990bc38"
+dependencies = [
+ "futures-util",
+ "log",
+ "native-tls",
+ "tokio",
+ "tokio-native-tls",
+ "tungstenite 0.21.0",
+]
+
 [[package]]
 name = "tokio-tungstenite"
 version = "0.24.0"
@@ -2604,7 +2618,7 @@ dependencies = [
  "native-tls",
  "tokio",
  "tokio-native-tls",
- "tungstenite",
+ "tungstenite 0.24.0",
 ]
 
 [[package]]
@@ -2766,6 +2780,26 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "tungstenite"
+version = "0.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ef1a641ea34f399a848dea702823bbecfb4c486f911735368f1f137cb8257e1"
+dependencies = [
+ "byteorder",
+ "bytes",
+ "data-encoding",
+ "http",
+ "httparse",
+ "log",
+ "native-tls",
+ "rand 0.8.5",
+ "sha1",
+ "thiserror 1.0.69",
+ "url",
+ "utf-8",
+]
+
 [[package]]
 name = "tungstenite"
 version = "0.24.0"
@@ -2943,7 +2977,7 @@ dependencies = [
  "sha2",
  "sled",
  "tokio",
- "tokio-tungstenite",
+ "tokio-tungstenite 0.24.0",
  "tracing",
  "tracing-subscriber",
  "url",
@@ -3008,6 +3042,7 @@ dependencies = [
  "sled",
  "thiserror 2.0.18",
  "tokio",
+ "tokio-tungstenite 0.21.0",
  "tower 0.4.13",
  "tower-http 0.5.2",
  "tracing",