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>

ui/app.go

@@ -0,0 +1,15 @@
+package ui
+
+import (
+	_ "syscall/js"
+
+	"git.flowmade.one/flowmade-one/iris/internal/element"
+)
+
+func NewApp(view View) {
+	app := NewView()
+	app.e.Grid()
+	app.MinHeight("100vh")
+	app.Child(view)
+	element.Mount(app.e)
+}