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)

crates/rampart-core/build.rs

@@ -1,43 +0,0 @@
-use std::path::PathBuf;
-use std::process::Command;
-
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let has_xdp_feature = std::env::var("CARGO_FEATURE_XDP").is_ok();
-    if !has_xdp_feature {
-        return Ok(());
-    }
-
-    let manifest_dir = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?);
-    let xdp_dir = manifest_dir.join("../../xdp");
-    let out_dir = PathBuf::from(std::env::var("OUT_DIR")?);
-
-    let src = xdp_dir.join("xdp_filter.c");
-    let dst = out_dir.join("xdp_filter.o");
-
-    println!("cargo:rerun-if-changed={}", src.display());
-
-    let host_triple = std::env::var("HOST").unwrap_or_default();
-    let arch = host_triple.split('-').next().unwrap_or(&host_triple);
-    let status = Command::new("clang")
-        .args([
-            "-O2",
-            "-g",
-            "-target",
-            "bpf",
-            "-mcpu=v3",
-            "-c",
-            src.to_str().ok_or("src path is not valid UTF-8")?,
-            "-o",
-            dst.to_str().ok_or("dst path is not valid UTF-8")?,
-            &format!("-I{}", xdp_dir.display()),
-            &format!("-I/usr/include/{}-linux-gnu", arch),
-        ])
-        .status()?;
-
-    if !status.success() {
-        return Err("XDP C compilation failed (see clang errors above)".into());
-    }
-
-    println!("cargo:rerun-if-env-changed=CARGO_FEATURE_XDP");
-    Ok(())
-}