templates: migrate OIDC callback to elem-go

Replace html/template with type-safe elem-go templating for OIDC
callback page. Improves consistency with other templates and provides
compile-time safety. All UI elements and styling preserved.

hscontrol/templates/general.go

@@ -6,6 +6,8 @@ import (
 	"github.com/chasefleming/elem-go/styles"
 )
 
+// bodyStyle provides consistent body styling across all templates with
+// a centered, readable layout and appropriate spacing.
 var bodyStyle = styles.Props{
 	styles.Margin:     "40px auto",
 	styles.MaxWidth:   "800px",
@@ -13,31 +15,35 @@ var bodyStyle = styles.Props{
 	styles.FontSize:   "16px",
 	styles.Color:      "#444",
 	styles.Padding:    "0 10px",
-	styles.FontFamily: "Sans-serif",
+	styles.FontFamily: "sans-serif",
 }
 
+// headerStyle provides consistent header styling with improved line height
 var headerStyle = styles.Props{
 	styles.LineHeight: "1.2",
 }
 
+// headerOne creates a level 1 heading with consistent styling
 func headerOne(text string) *elem.Element {
 	return elem.H1(attrs.Props{attrs.Style: headerStyle.ToInline()}, elem.Text(text))
 }
 
+// headerTwo creates a level 2 heading with consistent styling
 func headerTwo(text string) *elem.Element {
 	return elem.H2(attrs.Props{attrs.Style: headerStyle.ToInline()}, elem.Text(text))
 }
 
+// headerThree creates a level 3 heading with consistent styling
 func headerThree(text string) *elem.Element {
 	return elem.H3(attrs.Props{attrs.Style: headerStyle.ToInline()}, elem.Text(text))
 }
 
+// HtmlStructure creates a complete HTML document structure with proper meta tags
+// and semantic HTML5 structure. The head and body elements are passed as parameters
+// to allow for customization of each page.
 func HtmlStructure(head, body *elem.Element) *elem.Element {
-	return elem.Html(nil,
-		elem.Head(
-			attrs.Props{
-				attrs.Lang: "en",
-			},
+	return elem.Html(attrs.Props{attrs.Lang: "en"},
+		elem.Head(nil,
 			elem.Meta(attrs.Props{
 				attrs.Charset: "UTF-8",
 			}),