feat(stats): add migration v7 visit table and client-ip helpers

reaction_board/migrations.py

@@ -224,6 +224,26 @@ MIGRATIONS: tuple[Migration, ...] = (
             "ALTER TABLE video ADD COLUMN up_face TEXT",
         ),
     ),
+    Migration(
+        version=7,
+        name="visit access statistics",
+        statements=(
+            # 访问统计按 (日期, IP, 路由) 聚合：PV = SUM(hits)，UV = COUNT(DISTINCT ip)。
+            # 数据先落内存缓冲、批量 upsert，因此 hits 累加而非逐条插入。
+            """
+            CREATE TABLE visit (
+              stat_date TEXT NOT NULL,
+              ip        TEXT NOT NULL,
+              path      TEXT NOT NULL,
+              hits      INTEGER NOT NULL DEFAULT 0,
+              first_at  INTEGER NOT NULL,
+              last_at   INTEGER NOT NULL,
+              PRIMARY KEY (stat_date, ip, path)
+            )
+            """,
+            "CREATE INDEX idx_visit_date ON visit(stat_date)",
+        ),
+    ),
 )