Add Obsidian Toolbox — 4 syntax generators under /tools

Inside-LMS toolbox for registered students: callout-CSS, YAML-frontmatter,
theme CSS-variables, Style Settings generators. Auth inherited from (student)
route group; no public surface, no email gate.

- Pure generators in src/lib/tools/* with Vitest (33 tests)
- Shared YAML-safe scalar quoter (_shared/yaml.ts) used by frontmatter +
  style-settings: unquoted user input was silently breaking YAML (tags '#x'
  -> null, color default '#7C3AED' -> null, 'a: b' -> parse error)
- hex validation in callout (no NaN), date input constrained, clipboard +
  analytics calls guarded
- Prisma ToolUsage model + migration; logToolUsage Server Action (auth-first,
  10-min dedup window per user/tool)
- Tool index /tools + ToolCard (explicit lucide map, no import *) + header link

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/tools/ToolCard.tsx

@@ -0,0 +1,24 @@
+import Link from "next/link";
+import { MessageSquareQuote, FileCode2, Palette, SlidersHorizontal, Wrench, type LucideIcon } from "lucide-react";
+import type { ToolMeta } from "@/lib/tools/_shared/types";
+
+// Явная карта (не `import * as Icons`) — иначе весь набор lucide попадает в бандл.
+const ICONS: Record<string, LucideIcon> = {
+  MessageSquareQuote,
+  FileCode2,
+  Palette,
+  SlidersHorizontal,
+};
+
+export function ToolCard({ tool }: { tool: ToolMeta }) {
+  const Icon = ICONS[tool.icon] ?? Wrench;
+  return (
+    <Link href={`/tools/${tool.id}`} className="card-aubade p-4 flex flex-col gap-2 no-underline">
+      <div className="flex items-center gap-2" style={{ color: "var(--foreground)" }}>
+        <Icon size={20} />
+        <span className="font-bold">{tool.title}</span>
+      </div>
+      <p className="text-sm" style={{ color: "var(--muted-foreground)" }}>{tool.description}</p>
+    </Link>
+  );
+}