fix(HEL-494): 盘中双免费源故障切换并禁止问天假0覆盖

主源东财失败后自动改走腾讯行情，成功结果写入缓存；两源都失败时返回最近真实快照并标明延迟，不再显示假0。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

config/architecture-inventory.json

@@ -486,6 +486,11 @@
       "bytes": 48447,
       "lines": 665
     },
+    {
+      "path": "backend/data/providers/tushare_industries.py",
+      "bytes": 38757,
+      "lines": 892
+    },
     {
       "path": "backend/features/screener/catalog.py",
       "bytes": 35571,
@@ -498,13 +503,8 @@
     },
     {
       "path": "backend/data/providers/tushare_dashboard.py",
-      "bytes": 34631,
-      "lines": 812
-    },
-    {
-      "path": "backend/data/providers/tushare_industries.py",
-      "bytes": 33324,
-      "lines": 766
+      "bytes": 34773,
+      "lines": 815
     },
     {
       "path": "database.py",
@@ -538,8 +538,8 @@
     },
     {
       "path": "backend/features/heaven/trend.py",
-      "bytes": 16772,
-      "lines": 370
+      "bytes": 17005,
+      "lines": 373
     },
     {
       "path": "backend/features/market/insights_auction_scoring.py",
@@ -573,8 +573,8 @@
     },
     {
       "path": "backend/features/heaven/market_context.py",
-      "bytes": 13687,
-      "lines": 338
+      "bytes": 14409,
+      "lines": 354
     },
     {
       "path": "frontend/shared/session.js",
@@ -801,16 +801,16 @@
       "bytes": 2299,
       "lines": 57
     },
+    {
+      "path": "backend/data/providers/tushare_client.py",
+      "bytes": 2263,
+      "lines": 70
+    },
     {
       "path": "backend/features/screener/regime.py",
       "bytes": 2202,
       "lines": 53
     },
-    {
-      "path": "backend/data/providers/tushare_client.py",
-      "bytes": 2166,
-      "lines": 68
-    },
     {
       "path": "frontend/pages/popularity/page.html",
       "bytes": 2165,