feat: add Random Generator tool

Cryptographically secure generator for 5 types:
- Password: configurable charset + entropy strength meter
- UUID: crypto.randomUUID()
- API Key: hex/base62/base64url with optional prefix
- Hash: SHA-1/256/512 of custom input or random data
- Token: variable byte-length in hex or base64url

All using Web Crypto API — nothing leaves the browser.
Registered in lib/tools.tsx with RandomIcon (dice).

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

lib/random/generators.ts

@@ -0,0 +1,118 @@
+const CHARSET = {
+  uppercase: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
+  lowercase: 'abcdefghijklmnopqrstuvwxyz',
+  numbers: '0123456789',
+  symbols: '!@#$%^&*()-_=+[]{}|;:,.<>?',
+  hex: '0123456789abcdef',
+  base62: '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz',
+};
+
+export interface PasswordOpts {
+  length: number;
+  uppercase: boolean;
+  lowercase: boolean;
+  numbers: boolean;
+  symbols: boolean;
+}
+
+export interface ApiKeyOpts {
+  length: number;
+  format: 'hex' | 'base62' | 'base64url';
+  prefix: string;
+}
+
+export interface HashOpts {
+  algorithm: 'SHA-1' | 'SHA-256' | 'SHA-512';
+  input: string;
+}
+
+export interface TokenOpts {
+  bytes: number;
+  format: 'hex' | 'base64url';
+}
+
+function randomBytes(n: number): Uint8Array {
+  const arr = new Uint8Array(n);
+  crypto.getRandomValues(arr);
+  return arr;
+}
+
+function toHex(bytes: Uint8Array): string {
+  return Array.from(bytes)
+    .map((b) => b.toString(16).padStart(2, '0'))
+    .join('');
+}
+
+function toBase64url(bytes: Uint8Array): string {
+  return btoa(String.fromCharCode(...bytes))
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=/g, '');
+}
+
+export function generatePassword(opts: PasswordOpts): string {
+  let charset = '';
+  if (opts.uppercase) charset += CHARSET.uppercase;
+  if (opts.lowercase) charset += CHARSET.lowercase;
+  if (opts.numbers) charset += CHARSET.numbers;
+  if (opts.symbols) charset += CHARSET.symbols;
+  if (!charset) charset = CHARSET.lowercase + CHARSET.numbers;
+
+  const bytes = randomBytes(opts.length * 4);
+  let result = '';
+  let i = 0;
+  while (result.length < opts.length && i < bytes.length) {
+    const idx = bytes[i] % charset.length;
+    result += charset[idx];
+    i++;
+  }
+  return result.slice(0, opts.length);
+}
+
+export function passwordEntropy(opts: PasswordOpts): number {
+  let size = 0;
+  if (opts.uppercase) size += 26;
+  if (opts.lowercase) size += 26;
+  if (opts.numbers) size += 10;
+  if (opts.symbols) size += CHARSET.symbols.length;
+  if (size === 0) size = 36;
+  return Math.round(Math.log2(size) * opts.length);
+}
+
+export function generateUUID(): string {
+  return crypto.randomUUID();
+}
+
+export function generateApiKey(opts: ApiKeyOpts): string {
+  const bytes = randomBytes(opts.length * 2);
+  let key: string;
+  switch (opts.format) {
+    case 'hex':
+      key = toHex(bytes).slice(0, opts.length);
+      break;
+    case 'base64url':
+      key = toBase64url(bytes).slice(0, opts.length);
+      break;
+    case 'base62': {
+      const cs = CHARSET.base62;
+      key = Array.from(bytes)
+        .map((b) => cs[b % cs.length])
+        .join('')
+        .slice(0, opts.length);
+      break;
+    }
+  }
+  return opts.prefix ? `${opts.prefix}_${key}` : key;
+}
+
+export async function generateHash(opts: HashOpts): Promise<string> {
+  const data = opts.input.trim() || toHex(randomBytes(32));
+  const encoded = new TextEncoder().encode(data);
+  const hashBuffer = await crypto.subtle.digest(opts.algorithm, encoded);
+  return toHex(new Uint8Array(hashBuffer));
+}
+
+export function generateToken(opts: TokenOpts): string {
+  const bytes = randomBytes(opts.bytes);
+  return opts.format === 'hex' ? toHex(bytes) : toBase64url(bytes);
+}