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)

.gitignore

@@ -34,24 +34,7 @@ Thumbs.db
 *.so
 *.d
 
-# Java / Gradle
-plugins/*/build/
-plugins/*/.gradle/
-plugins/*/bin/
-plugins/*/.classpath
-plugins/*/.project
-plugins/*/.settings/
-plugins/*/.factorypath
-plugins/.gradle/
-plugins/.project
-plugins/.settings/
-plugins/build/
 *.jar
-!plugins/gradle/wrapper/gradle-wrapper.jar
-
-# Dashboard build
-dashboard/dist/
-dashboard/node_modules/
 
 # Eclipse / IDE
 .classpath
@@ -62,6 +45,3 @@ bin/
 
 # Reference projects (cloned for research)
 ref/
-
-# Paper jar cache
-deploy/docker/downloads/