feat: initial implementation of go-kite

Core framework:
- Kite router with full HTTP method support (GET, POST, PUT, DELETE, HEAD, OPTIONS, CONNECT, TRACE)
- Nestable route groups with prefix and middleware inheritance
- Global, group, and route-level middleware with onion ordering
- Centralized error, not-found, and method-not-allowed handlers
- Graceful shutdown on SIGTERM/SIGINT with configurable timeout
- Configurable server read, write, and idle timeouts
- Context with typed request/response helpers, value store, cookie, form, and body binding support
- Response writer wrapper for status code tracking

Middleware:
- Logger with configurable output, format, and skip function
- Recovery with configurable panic handler
- RequestID with configurable header and generator, forwards incoming IDs
- CORS with configurable origins, methods, headers, credentials, and max age
- MaxBodySize with configurable byte limit

Docs:
- README with quickstart, routing, middleware, context API reference, and TLS guide

not_found_handler.go

@@ -0,0 +1,9 @@
+package kite
+
+import "net/http"
+
+type NotFoundHandler Handler
+
+func defaultNotFoundHandler(ctx *Context) error {
+	return ctx.WriteString(http.StatusNotFound, "404 not found")
+}