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/font.go

@@ -0,0 +1,42 @@
+package ui
+
+type Font struct {
+	family     string
+	size       string
+	weight     string
+	lineheight string
+}
+
+func NewFont() Font {
+	return Font{
+		family:     "sans-serif",
+		size:       "16px",
+		weight:     "400",
+		lineheight: "20px",
+	}
+}
+
+func (f Font) Family(family string) Font {
+	f.family = family
+	return f
+}
+
+func (f Font) Size(size string) Font {
+	f.size = size
+	return f
+}
+
+func (f Font) Weight(weight string) Font {
+	f.weight = weight
+	return f
+}
+
+func (f Font) String() string {
+	return f.weight + " " + f.size + " " + f.family + ""
+}
+
+// todo we can't apply this straight via the css, we need to apply it to the lineheight of the parent
+func (f Font) LineHeight(lineheight string) Font {
+	f.lineheight = lineheight
+	return f
+}