Initial iris repository structure

WASM reactive UI framework for Go:
- reactive/ - Signal[T], Effect, Runtime
- ui/ - Button, Text, Input, View, Canvas, SVG components
- navigation/ - Router, guards, history management
- auth/ - OIDC client for WASM applications
- host/ - Static file server

Extracted from arcadia as open-source component.

Co-Authored-By: Claude <noreply@anthropic.com>

Makefile

@@ -0,0 +1,16 @@
+.PHONY: build build-wasm test lint clean
+
+build: build-wasm
+	go build ./host/...
+
+build-wasm:
+	GOOS=js GOARCH=wasm go build ./...
+
+test:
+	go test ./...
+
+lint:
+	golangci-lint run
+
+clean:
+	rm -f *.wasm