feat(panel): default light background is white, not gray

Plain light mode no longer uses a gray-blue page background so the blue
accent cannot blend in; the themed variant tints white instead.

src/internal/panel/panel_test.go

@@ -350,8 +350,8 @@ func TestOverviewThemeColor(t *testing.T) {
 	if !strings.Contains(plain, "--accent:#2563eb") {
 		t.Error("plain overview should keep the default accent")
 	}
-	if !strings.Contains(plain, "--bg:#e6ebf1") {
-		t.Error("plain overview light background should be the darker shade")
+	if !strings.Contains(plain, "--bg:#ffffff") {
+		t.Error("plain overview light background should be white")
 	}
 
 	themed := srv.renderToString(t, "overview.html", pageData{
@@ -361,7 +361,7 @@ func TestOverviewThemeColor(t *testing.T) {
 	})
 	for _, want := range []string{
 		"--accent:#16a34a", "--head:#16a34a",
-		"color-mix(in srgb, #16a34a 13%, #e6ebf1)",
+		"color-mix(in srgb, #16a34a 13%, #ffffff)",
 		"color-mix(in srgb, #16a34a 16%, #14161a)",
 		"color-mix(in srgb, #16a34a 5%, #ffffff)",
 		"border-bottom:3px solid #16a34a",

src/internal/panel/templates/login.html

@@ -6,7 +6,7 @@
 <title>{{.Title}}</title>
 <style>
 :root{
-  --bg:#e6ebf1; --card:#ffffff; --border:#e2e8f0; --text:#0f172a; --muted:#64748b;
+  --bg:#ffffff; --card:#ffffff; --border:#e2e8f0; --text:#0f172a; --muted:#64748b;
   --accent:#2563eb; --on-accent:#fff; --err-bg:#fef2f2; --err-fg:#dc2626;
   color-scheme:light;
 }

src/internal/panel/templates/overview.html

@@ -6,7 +6,7 @@
 <title>{{.Title}}</title>
 <style>
 :root{
-  --bg:#e6ebf1; --card:#ffffff; --border:#e2e8f0; --text:#0f172a; --muted:#64748b;
+  --bg:#ffffff; --card:#ffffff; --border:#e2e8f0; --text:#0f172a; --muted:#64748b;
   --head:#0284c7; --accent:#2563eb; --on-accent:#fff;
   --accent-soft:rgba(37,99,235,.12); --accent-glow:rgba(37,99,235,.30);
   --ok:#059669; --ok-bg:#ecfdf5; --ok-fg:#047857;
@@ -178,7 +178,7 @@ footer a{color:var(--muted);text-decoration:underline}
   --on-accent:#fff;
   --accent-soft:color-mix(in srgb, {{.ThemeColor}} 18%, transparent);
   --accent-glow:color-mix(in srgb, {{.ThemeColor}} 45%, transparent);
-  --bg:color-mix(in srgb, {{.ThemeColor}} 13%, #e6ebf1);
+  --bg:color-mix(in srgb, {{.ThemeColor}} 13%, #ffffff);
   --card:color-mix(in srgb, {{.ThemeColor}} 5%, #ffffff);
   --border:color-mix(in srgb, {{.ThemeColor}} 24%, #e2e8f0);
   --code-bg:color-mix(in srgb, {{.ThemeColor}} 8%, #f8fafc);