feat: 需求池重构 + 联动引擎 + 开发状态推导

架构：新建 lib/linkage-engine.ts 联动引擎
- deriveReqDevStatus(): 从 devTasks 推导需求开发状态
- canEditRequirement(): 开发中的需求不可编辑
- checkVersionChangeRisk(): 版本变更风险检查
- 所有跨模块推导逻辑集中在此文件

功能改动：
1. 导航改名"需求"→"需求池"
2. 新建需求：所属产品/项目必填，移除产品负责人字段
3. 需求表格新增"开发状态"列：
   未排期/待开发/开发中/已完成（从 devTasks 实时推导）
4. 开发中的需求：编辑按钮禁用
5. 需求设 versionId → 版本详情关联需求天然兼容
   （版本详情通过 filter(r.versionId === versionId) 读取）

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

apps/web/app/requirements/page.tsx

@@ -4,9 +4,11 @@ import { useEffect, useMemo, useState } from 'react';
 import { Search, Plus, Lightbulb, ArrowUp, ArrowDown } from 'lucide-react';
 import { useRequirementStore } from '@/stores/useRequirementStore';
 import { useProductStore } from '@/stores/useProductStore';
+import { useDevTaskStore } from '@/stores/useDevTaskStore';
 import { flattenProjects, flattenVersions } from '@/lib/derive';
 import { REQ_STATUS_LABEL, REQ_STATUS_COLOR, SOURCE_TYPE_LABEL } from '@/lib/requirement';
 import type { Requirement, RequirementStatus, SourceType } from '@/lib/requirement';
+import { deriveReqDevStatus, canEditRequirement, REQ_DEV_STATUS_LABEL, REQ_DEV_STATUS_COLOR } from '@/lib/linkage-engine';
 import { Pagination, usePagination } from '@/components/Pagination';
 import { RequirementModal } from '@/components/requirement/RequirementModal';
 import { RequirementDetail } from '@/components/requirement/RequirementDetail';
@@ -42,6 +44,7 @@ export default function RequirementsPage() {
     addPlatform, updatePlatform, deletePlatform,
   } = useRequirementStore();
   const { overview, fetchOverview } = useProductStore();
+  const { tasks: devTasks, fetchTasks: fetchDevTasks } = useDevTaskStore();
   const allProjects = useMemo(() => flattenProjects(overview), [overview]);
   const allVersions = useMemo(() => flattenVersions(overview), [overview]);
 
@@ -62,6 +65,7 @@ export default function RequirementsPage() {
 
   useEffect(() => { fetchOverview(); }, [fetchOverview]);
   useEffect(() => { fetchRequirements(); }, [fetchRequirements]);
+  useEffect(() => { fetchDevTasks(); }, [fetchDevTasks]);
 
   // Resolve version name from overview
   const resolveVersionName = (versionId?: string): string => {
@@ -249,7 +253,7 @@ export default function RequirementsPage() {
                       <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">状态</th>
                       <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">优先级</th>
                       <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">所属版本</th>
-                      <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">产品负责人</th>
+                      <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">开发状态</th>
                       <th className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)]">录入人员</th>
                       <th
                         className="px-4 py-2.5 text-[11px] font-medium uppercase tracking-wide text-[var(--ink-muted)] cursor-pointer select-none hover:text-[var(--ink-soft)] transition-colors"
@@ -314,9 +318,16 @@ export default function RequirementsPage() {
                           {resolveVersionName(req.versionId)}
                         </td>
 
-                        {/* 产品负责人 */}
-                        <td className="px-4 py-3 text-[12px] text-[var(--ink-soft)]">
-                          {req.productOwner || '-'}
+                        {/* 开发状态 */}
+                        <td className="px-4 py-3">
+                          {(() => {
+                            const devStatus = deriveReqDevStatus(req.id, devTasks);
+                            return (
+                              <span className={`inline-flex items-center rounded-md px-2 py-0.5 text-[10px] font-medium ${REQ_DEV_STATUS_COLOR[devStatus]}`}>
+                                {REQ_DEV_STATUS_LABEL[devStatus]}
+                              </span>
+                            );
+                          })()}
                         </td>
 
                         {/* 录入人员 */}
@@ -332,8 +343,8 @@ export default function RequirementsPage() {
                         {/* 操作 */}
                         <td className="px-4 py-3 text-right" onClick={(e) => e.stopPropagation()}>
                           <div className="flex items-center justify-end gap-1">
-                            {/* 编辑：待评审/已采纳/已规划 */}
-                            {(['pending_review', 'adopted', 'planned'] as const).includes(req.status as any) && (
+                            {/* 编辑：待评审/已采纳/已规划，且开发中不可编辑 */}
+                            {(['pending_review', 'adopted', 'planned'] as const).includes(req.status as any) && canEditRequirement(req.id, devTasks) && (
                               <button
                                 onClick={() => handleEdit(req)}
                                 className="h-6 px-2 rounded text-[11px] font-medium text-[var(--ink-soft)] hover:bg-[var(--bg-subtle)] transition-colors"