feat: DB-first architecture with lock-safe writes

- price_monitor: writes live prices to both JSON and mofin.db (holdings + live_prices + portfolio_summary)
- mofin_db: added execute_with_retry/commit_with_retry with exponential backoff on 'database is locked'
- mofin_db: increased timeout 5s->15s, added PRAGMA busy_timeout=15000
- price_monitor retry loop: fixed break-before-if-ok bug (was not retrying on write failure)
- DB connection: WAL mode + retry decorator for all write operations
- cash sync: preserves DB authoritative cash (JSON cash not pushed to DB)

This is the DB-first version. JSON writes remain for dashboard compatibility.
Next step: remove JSON writes entirely for full DB-only architecture.

data/stocks/02202.json

@@ -621,6 +621,16 @@
       "content": "- **万科(02202)** — 现价2.20，止损2.00（距9%）。周五港股继续弱，若跌破2.00港币将触发止损。建议：提前制定应对方案，而不是等到触发了再慌。",
       "report_id": "cron_e02b8bde74f8_2026-06-28_22-11-21"
     },
+    {
+      "time": "2026-07-06T08:55:01.761812",
+      "content": "3. **0714止盈策略严重过期** — 当前 19 个持仓中有约 13 个（68%）的成本价高于止盈价，说明策略数据已随股价下跌严重偏离，大量止损/止盈位明显陈旧（如万科 02202 成本 ¥4.",
+      "report_id": "cron_e02b8bde74f8_2026-07-05_22-05-42"
+    },
+    {
+      "time": "2026-07-06T08:55:01.761812",
+      "content": "3. **策略数据翻新** — 针对成本远高于止盈的 13 个持仓（如 万科02202、比亚迪01211、华恒生物688639、中科电气300035、黄金ETF518880 等），建议逐个审核是否需要",
+      "report_id": "cron_e02b8bde74f8_2026-07-05_22-05-42"
+    },
     {
       "time": "2026-06-04T09:55:40.300986",
       "content": "- 万科(02202): 补仓区间2.5~2.6，昨收2.70，距+3.8%，未进入。",