feat: INP2P v0.1.0 — complete P2P tunneling system

Core modules (M1-M6):
- pkg/protocol: message format, encoding, NAT type enums
- pkg/config: server/client config structs, env vars, validation
- pkg/auth: CRC64 token, TOTP gen/verify, one-time relay tokens
- pkg/nat: UDP/TCP STUN client and server
- pkg/signal: WSS message dispatch, sync request/response
- pkg/punch: UDP/TCP hole punching + priority chain
- pkg/mux: stream multiplexer (7B frame: StreamID+Flags+Len)
- pkg/tunnel: mux-based port forwarding with stats
- pkg/relay: relay manager with TOTP auth + session bridging
- internal/server: signaling server (login/heartbeat/report/coordinator)
- internal/client: client (NAT detect/login/punch/relay/reconnect)
- cmd/inp2ps + cmd/inp2pc: main entrypoints with graceful shutdown

All tests pass: 16 tests across 5 packages
Code: 3559 lines core + 861 lines tests = 19 source files

.gitignore

@@ -0,0 +1,32 @@
+# Binaries
+bin/
+*.exe
+*.dll
+*.so
+*.dylib
+
+# Test binary
+*.test
+
+# Go workspace
+go.work
+go.work.sum
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Config files with secrets
+config.json
+config.yaml
+*.db
+*.sqlite
+
+# Temp
+/tmp/