docs: 统一文档与代码一致性

- 修复所有 confidence → subjective_confidence 残留(03-api, 04-agents, 05-data, 07-development)
- 修复 5 张表 → 6 张表残留(06-deployment)
- 同步 API schema 示例与实际模型一致
- 更新 predictions 表结构文档(新增 status/cutoff/input_hash 字段)

code: 修复 API 异常处理(eval/predict)和 context_builder stats 时间过滤

src/llm/context_builder.py

@@ -142,7 +142,7 @@ async def form_slice(header: MatchHeader, *, limit: int = 5, before=None) -> str
                 else: losses += 1
                 score = f"{fm.home_goals}-{fm.away_goals}" if fm.home_goals is not None else "vs"
                 xg = ""
-                if fm.stats and fm.stats.home_xg is not None:
+                if fm.stats and _is_stats_available(fm.stats, before) and fm.stats.home_xg is not None:
                     own = fm.stats.home_xg if side == "home" else fm.stats.away_xg
                     xg = f" (xG {own:.1f})"
                 opp = fm.away_team.name if side == "home" else fm.home_team.name