feat(test-case+bug): 测试用例模块 + Bug 模块完整实现

需求验收体系：
- 测试用例：五态状态机（待执行/执行中/通过/失败/阻塞）
- Bug：六态状态机（待修复/修复中/已修复/验证中/已关闭/已拒绝）
- Bug 通过测试用例间接关联需求（不冗余存版本）
- Bug 默认修复人 = 关联需求的开发任务负责人
- 测试进度 = 已执行用例/总用例, 通过率 = 通过/已执行

UI:
- 版本详情页新增"测试用例" Tab + "BUG" Tab
- 测试用例：统计栏+筛选+按需求分组列表+详情抽屉+提BUG入口
- Bug：统计栏+筛选+列表+详情抽屉（链式跳转用例→需求）
- 概览胶囊"测试"阶段进度联动
- "与我相关"新增测试用例/Bug分组

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/lib/bug.ts

@@ -0,0 +1,75 @@
+import type { Priority } from './derive';
+
+export type BugStatus = 'open' | 'fixing' | 'fixed' | 'verifying' | 'closed' | 'rejected';
+export type BugSeverity = 'critical' | 'major' | 'minor' | 'trivial';
+
+export interface Bug {
+  id: string;
+  bugNo: string;
+  testCaseId: string;
+  title: string;
+  description: string;
+  severity: BugSeverity;
+  priority: Priority;
+  reportedBy: string;
+  assigneeId: string;
+  status: BugStatus;
+  resolvedAt?: string;
+  closedAt?: string;
+  resolution?: string;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export const BUG_STATUS_LABEL: Record<BugStatus, string> = {
+  open: '待修复',
+  fixing: '修复中',
+  fixed: '已修复',
+  verifying: '验证中',
+  closed: '已关闭',
+  rejected: '已拒绝',
+};
+
+export const BUG_STATUS_COLOR: Record<BugStatus, string> = {
+  open: 'bg-red-50 text-red-600',
+  fixing: 'bg-blue-50 text-blue-600',
+  fixed: 'bg-indigo-50 text-indigo-600',
+  verifying: 'bg-purple-50 text-purple-600',
+  closed: 'bg-emerald-50 text-emerald-600',
+  rejected: 'bg-zinc-100 text-zinc-500',
+};
+
+export const BUG_SEVERITY_LABEL: Record<BugSeverity, string> = {
+  critical: '致命',
+  major: '严重',
+  minor: '一般',
+  trivial: '轻微',
+};
+
+export const BUG_SEVERITY_COLOR: Record<BugSeverity, string> = {
+  critical: 'bg-red-100 text-red-700',
+  major: 'bg-orange-50 text-orange-700',
+  minor: 'bg-yellow-50 text-yellow-700',
+  trivial: 'bg-zinc-100 text-zinc-600',
+};
+
+export const BUG_ALLOWED_TRANSITIONS: Record<BugStatus, BugStatus[]> = {
+  open: ['fixing', 'rejected'],
+  fixing: ['fixed'],
+  fixed: ['verifying'],
+  verifying: ['closed', 'open'],
+  closed: [],
+  rejected: [],
+};
+
+export function canBugTransition(from: BugStatus, to: BugStatus): boolean {
+  return BUG_ALLOWED_TRANSITIONS[from].includes(to);
+}
+
+export function generateBugNo(existingBugs: Bug[]): string {
+  const maxNum = existingBugs.reduce((max, b) => {
+    const num = parseInt(b.bugNo.replace('BUG-', ''), 10);
+    return isNaN(num) ? max : Math.max(max, num);
+  }, 0);
+  return `BUG-${String(maxNum + 1).padStart(3, '0')}`;
+}