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/sc5.py

@@ -0,0 +1,12 @@
+import ast, sys
+files = ['price_monitor', 'strategy_feedback', 'system_health_check', 'mo_config', 'mofin_health']
+ok = True
+for f in files:
+    p = f'/home/hmo/MoFin/deploy/profile-scripts/{f}.py'
+    try:
+        ast.parse(open(p).read())
+        print('OK', f)
+    except SyntaxError as e:
+        print('FAIL', f, e)
+        ok = False
+sys.exit(0 if ok else 1)