refactor: centralize numeric normalization

app/config/architecture-inventory.json

@@ -220,6 +220,16 @@
       "runtime_role": "index observation fallback"
     }
   ],
+  "numeric_normalization": [
+    {
+      "function": "finite_number",
+      "path": "backend/data/numbers.py"
+    },
+    {
+      "function": "non_nan_number",
+      "path": "backend/data/numbers.py"
+    }
+  ],
   "llm_entrypoints": [
     {
       "function": "stream_with_mentor",
@@ -279,13 +289,13 @@
     },
     {
       "path": "backend/features/screener/engine.py",
-      "bytes": 108552,
-      "lines": 2213
+      "bytes": 108394,
+      "lines": 2206
     },
     {
       "path": "backend/data/providers/tushare_client.py",
-      "bytes": 94329,
-      "lines": 2175
+      "bytes": 94171,
+      "lines": 2168
     },
     {
       "path": "frontend/app.js",
@@ -314,8 +324,8 @@
     },
     {
       "path": "backend/features/market/insights.py",
-      "bytes": 58150,
-      "lines": 1314
+      "bytes": 57998,
+      "lines": 1307
     },
     {
       "path": "frontend/pages/market/runtime.js",