feat: crypto library, Nexus HTTP server, JWT CLI, Boko web framework

- lib/crypto/: 9-module crypto library (Hash, HMAC, Base64/URL, Random, AES, RSA, ECDSA, Ed25519, JWT)
- rt/runtime.c: +346 lines OpenSSL crypto primitives (SHA-1/384/512, HMAC, Base64URL, AES-CBC/GCM, RSA, ECDSA, Ed25519)
- apps/nexus/: multi-threaded HTTP/1.1 + HTTP/2 detect + WebSocket server
- apps/jwt-pitbul/: JWT CLI tool (sign, verify, decode, keygen)
- apps/boko-framework/: FastAPI-inspired async web framework
- test_crypto/: crypto library test suite (23 tests)

apps/nexus/bux.toml

@@ -0,0 +1,8 @@
+[Package]
+Name    = "nexus"
+Version = "0.1.0"
+Type    = "bin"
+Description = "High-performance multi-threaded HTTP/1.1, HTTP/2 and WebSocket server"
+
+[Build]
+Output = "Bin"