refactor: retire price_events.json completely — DB is the only store

User directive: no JSON, retire it fully, fix all related code.

Changes:
- price_monitor.py: record_event writes DB only; removed EVENTS_PATH/
  load_events/save_events entirely
- strategy_feedback.py: price events read from DB only (removed JSON fallback)
- system_health_check.py: removed price_events.json from file-check list,
  DB-only event stats (was showing 0/0 due to wrong-DB resolution)
- mo_config.py: removed dead price_events_path property (no callers)
- mofin_health.py: price_events freshness reads DB table (authoritative now)
- mofin_db.py: DATA_DIR/DB_PATH now ABSOLUTE (/home/hmo/MoFin/data) —
  was relative __file__.parent, so each hardlinked copy of mofin_db.py
  resolved to a DIFFERENT database (canonical vs web-dashboard vs
  profile-local third DB with 0 rows of everything except market_snapshots).
  This fragmentation was the real cause of health checks reading empty tables.
- Unified all 4 mofin_db copies (root/scripts/deploy/profile) via hardlink
- price_events.json archived to trashbox (fully backfilled: 6353 rows in DB)

Verified:
- record_event lands in DB only, JSON not recreated
- system_health_check: 历史事件 6353 / 今日事件 2965 (was 0/0)
- strategy_feedback + price_monitor full runs clean

scripts/mo_config.py

@@ -65,11 +65,6 @@ class MoConfig:
         warnings.warn("watchlist_path is deprecated — use mo_data.read_watchlist() for DB data", DeprecationWarning, stacklevel=2)
         return Path()
 
-    @property
-    def price_events_path(self) -> Path:
-        """⚠️ 已废弃！数据在 mofin.db price_events 表。"""
-        return self.data_dir / "price_events.json"
-    
     @property
     def live_prices_path(self) -> Path:
         """⚠️ DEPRECATED: 实时价格已迁移到 mofin_db.live_prices 表。"""