fix(combat): handle JSON string from DB (double-encoded stats_data)

The combat_stats DB column stores stats_data as JSON, but SQLAlchemy
returns it as a string (not a parsed dict). This caused:
- _combat_lifetime_cache loaded a string, merge failed silently
- API endpoints returned string instead of object for lifetime
- Frontend saw lifetime as a string, couldn't read .monsters

Fix: parse JSON string with json.loads() wherever stats_data is read
from DB — in the lifetime cache loader, single-character endpoint,
and all-characters endpoint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.py

@@ -1752,10 +1752,17 @@ async def get_combat_stats(character_name: str):
     )
     if not row:
         return {"character_name": character_name, "session": None, "lifetime": None}
+    sd = row["stats_data"]
+    if isinstance(sd, str):
+        import json as _json
+        try:
+            sd = _json.loads(sd)
+        except Exception:
+            sd = None
     return {
         "character_name": character_name,
         "session": None,
-        "lifetime": row["stats_data"],
+        "lifetime": sd,
     }
 
 
@@ -1776,10 +1783,15 @@ async def get_all_combat_stats():
     rows = await database.fetch_all("SELECT character_name, stats_data FROM combat_stats")
     for r in rows:
         if r["character_name"] not in seen:
+            sd = r["stats_data"]
+            if isinstance(sd, str):
+                import json as _json
+                try: sd = _json.loads(sd)
+                except Exception: sd = None
             results.append({
                 "character_name": r["character_name"],
                 "session": None,
-                "lifetime": r["stats_data"],
+                "lifetime": sd,
             })
     results.sort(key=lambda x: x["character_name"])
     return {"stats": results}
@@ -3028,7 +3040,18 @@ async def ws_receive_snapshots(
                                     "SELECT stats_data FROM combat_stats WHERE character_name = :n",
                                     {"n": char},
                                 )
-                                _combat_lifetime_cache[char] = row["stats_data"] if row else {}
+                                if row and row["stats_data"]:
+                                    sd = row["stats_data"]
+                                    # DB may return JSON as string — parse if needed
+                                    if isinstance(sd, str):
+                                        import json as _json
+                                        try:
+                                            sd = _json.loads(sd)
+                                        except Exception:
+                                            sd = {}
+                                    _combat_lifetime_cache[char] = sd
+                                else:
+                                    _combat_lifetime_cache[char] = {}
 
                             lifetime = _combat_merge_into_lifetime(
                                 _combat_lifetime_cache[char], delta