feat: icon-based formatting toolbar with dropdowns and link popover

Replace plain text toolbar labels with Lucide SVG icons. Group heading,
list, and alignment options into dropdown menus to reduce toolbar width.
Replace window.prompt link insertion with an inline popover (input, apply,
open, remove). Add underline and text-align TipTap extensions. Remove
task list from TipTap editor (broken styling). Fix task list bullet
rendering in note card preview. Increase editor min-height for markdown
mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app.html

@@ -1,14 +1,17 @@
 <!doctype html>
 <html lang="en">
-	<head>
-		<meta charset="utf-8" />
-		<meta name="viewport" content="width=device-width, initial-scale=1" />
-		<meta name="theme-color" content="#202124" />
-		<link rel="icon" href="%sveltekit.assets%/favicon.png" />
-		<title>Crumbs</title>
-		%sveltekit.head%
-	</head>
-	<body data-sveltekit-preload-data="hover">
-		<div style="display: contents">%sveltekit.body%</div>
-	</body>
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="theme-color" content="#202124" />
+    <link
+      rel="icon"
+      href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>🥨</text></svg>"
+    />
+    <title>Crumbs</title>
+    %sveltekit.head%
+  </head>
+  <body data-sveltekit-preload-data="hover">
+    <div style="display: contents">%sveltekit.body%</div>
+  </body>
 </html>