feat!: universal redesign — drop Minecraft stack, single-crate architecture

- remove Java plugins (velocity/paper), dashboard, all MC-specific code
  (handshake, death_code, varint, hostname-HMAC); available in history pre-v0.2
- merge crates/* into one package with src/bin/{rampart,rampart-manager,rampart-cli}
- ProtocolHandler trait + registry (no implementations yet), universal PoW kept
- XDP: universal L3/L4 filter (xdp/core/) + pluggable hook API (xdp/hooks/),
  fix IPv6 saddr bug; clang build verified
- docs: bilingual knowledge base (docs/kb/: attacks x4, defense-levels,
  practice x3), rewrite README/architecture for universal concept
- TODO.md v4.0: <=300-line module limit, competitor benchmark section (ref/)
- deploy/CI/docs cleanup: no MC references, new binary names

cargo build/clippy(-D warnings)/test green (55 tests)

deploy/docker-compose.yml

@@ -44,6 +44,7 @@ services:
       dockerfile: deploy/docker/Dockerfile.edge
     ports:
       - "25565:25565"
+      - "9090:9090"
     environment:
       RAMPART_CONFIG: /etc/rampart/config.toml
     volumes:
@@ -51,28 +52,3 @@ services:
     depends_on:
       redis:
         condition: service_healthy
-
-  velocity:
-    build:
-      context: ../..
-      dockerfile: deploy/docker/Dockerfile.velocity
-    environment:
-      RAMPART_HMAC_SECRET: test_secret_32_bytes_long_for_integration_test
-      RAMPART_ALLOWED_DOMAINS: play.example.com
-    ports:
-      - "25577:25577"
-    depends_on:
-      - paper
-
-  paper:
-    build:
-      context: ../..
-      dockerfile: deploy/docker/Dockerfile.paper
-    environment:
-      EULA: "true"
-      RAMPART_HMAC_SECRET: test_secret_32_bytes_long_for_integration_test
-      RAMPART_ALLOWED_DOMAINS: play.example.com
-    ports:
-      - "25566:25566"
-    depends_on:
-      - redis