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/CopyButton.tsx

@@ -0,0 +1,25 @@
+"use client";
+import { useState } from "react";
+import { Copy, Check } from "lucide-react";
+import { logToolUsage } from "@/lib/actions/tool-usage";
+import type { ToolId } from "@/lib/tools/_shared/types";
+
+export function CopyButton({ text, tool }: { text: string; tool: ToolId }) {
+  const [copied, setCopied] = useState(false);
+  async function onCopy() {
+    try {
+      await navigator.clipboard.writeText(text);
+    } catch {
+      return; // буфер недоступен (нет разрешения / insecure context) — молча
+    }
+    setCopied(true);
+    logToolUsage({ tool }).catch(() => {}); // аналитика — best-effort, не роняем UI
+    setTimeout(() => setCopied(false), 1500);
+  }
+  return (
+    <button type="button" onClick={onCopy} className="btn-aubade btn-aubade-accent inline-flex items-center gap-2 text-sm">
+      {copied ? <Check size={16} /> : <Copy size={16} />}
+      {copied ? "Скопировано" : "Скопировать"}
+    </button>
+  );
+}