feat: 交通信息与 AI 解耦，完善出发/回程路线显示

- 从 finalize_plan schema 和 agent 提示词中移除 transit 字段，AI 只负责活动/POI/坐标
- 新增 enrichTransitInfo：计划生成后查询高德 V3 公交 API，计算出发地→首活动、活动间、末活动→出发地三段交通
- parseTransitSegments 增加起终点站显示（去除线路名中的全程终点括号）
- WeekendPlanData 新增 transitFromStart/transitToEnd 字段
- BlindboxPlan 新增出发地和返回出发地交通连接器，传入 startLocationLabel 显示具体地址
- BlindBoxRoom schema 新增 address 字段存完整逆地理地址，city 保留供 API 使用
- 新增 /api/debug/transit 调试端点（仅开发环境）
- agent userPrompt 要求将出发/回程时间计入全天时间预算

src/components/BlindboxPlan.tsx

@@ -58,6 +58,8 @@ interface BlindboxPlanProps {
   onDaysChange?: (newDays: WeekendPlanData[]) => void;
   /** "lng,lat" 格式，用于 POI 搜索附近优先 */
   location?: string;
+  /** 出发地名称，用于显示在出发/返回连接器上 */
+  startLocationLabel?: string;
   onRefine?: (instruction: string) => Promise<void>;
 }
 
@@ -275,6 +277,7 @@ export default function BlindboxPlan({
   regenerating,
   onDaysChange,
   location,
+  startLocationLabel,
   onRefine,
 }: BlindboxPlanProps) {
   const [dayIndex, setDayIndex] = useState(0);
@@ -452,6 +455,21 @@ export default function BlindboxPlan({
                 items={currentDay.items.map((_, i) => `${dayIndex}-${i}`)}
                 strategy={verticalListSortingStrategy}
               >
+                {/* Transit from home to first activity */}
+                {currentDay.transitFromStart != null && (
+                  <div className="flex items-start gap-1.5 py-2 pl-1">
+                    <Navigation size={9} className="mt-0.5 shrink-0 text-purple-400/40" />
+                    <div className="flex flex-col gap-0.5">
+                      <span className="text-[10px] font-medium text-dim">从{startLocationLabel ?? "出发地"}出发</span>
+                      {currentDay.transitFromStartDescription && (
+                        <span className="text-[10px] leading-snug text-dim">
+                          {currentDay.transitFromStartDescription}
+                        </span>
+                      )}
+                      <span className="text-[10px] text-dim/70">约 {currentDay.transitFromStart} 分钟</span>
+                    </div>
+                  </div>
+                )}
                 {currentDay.items.map((item, i) => (
                   <motion.div
                     key={`${dayIndex}-${i}`}
@@ -483,6 +501,21 @@ export default function BlindboxPlan({
                         </div>
                       </div>
                     )}
+                    {/* Transit back home after last activity */}
+                    {i === currentDay.items.length - 1 && currentDay.transitToEnd != null && (
+                      <div className="flex items-start gap-1.5 py-2 pl-1">
+                        <Navigation size={9} className="mt-0.5 shrink-0 text-purple-400/40" />
+                        <div className="flex flex-col gap-0.5">
+                          <span className="text-[10px] font-medium text-dim">返回{startLocationLabel ?? "出发地"}</span>
+                          {currentDay.transitToEndDescription && (
+                            <span className="text-[10px] leading-snug text-dim">
+                              {currentDay.transitToEndDescription}
+                            </span>
+                          )}
+                          <span className="text-[10px] text-dim/70">约 {currentDay.transitToEnd} 分钟</span>
+                        </div>
+                      </div>
+                    )}
                   </motion.div>
                 ))}
               </SortableContext>