feat(billing): 计费商业化重构(积分制)+ 团队差异化调价

统一计价引擎 apps/billing/pricing.py:1积分=¥0.1,平台成本(¥)与用户价(积分)双记账,
视频按火山真实 usage.total_tokens 结算(true-up,终结¥1/段倒贴)+ 首发×1.5毛利系数。
Team.price_multiplier 差异化调价(jimeng同款):挂牌价×系数两步HALF_UP取整,视频类
按下单时的价格/汇率快照结算(中途改配不影响在途任务)。

BillingConfig 单例(汇率/毛利系数/预留buffer,admin可调即刻生效)。存量数据 ×10 rescale
迁移(RunPython+atomic,MySQL 迁移不可中断重跑)。开户赠送归零(DEFAULT_TRIAL_CREDITS=0,
商业决策)。audit_billing 加 I9(卖亏审计)。271 条测试 + tsc/build 全绿。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

core/backend/apps/accounts/migrations/0008_points_rescale.py

@@ -0,0 +1,38 @@
+"""积分制切换 · 限额字段 ×10(与 billing/0004 同窗口)。
+
+- TeamMember 三档限额:0=不限,0×10=0 语义不变;
+- Team.monthly_credit_limit:**-1 是「不限」哨兵,乘 10 变 -10 会破坏前端 === -1 判断**,
+  必须 WHERE > 0 才乘(0 保持不动);NULL 自然跳过;
+- Invitation.monthly_credit_limit:join_team 邀请码会把它落到新成员限额,漏乘会发 1/10 限额。
+
+写法纪律(review 修正):RunPython + atomic 防 MySQL 中断重放 ×100;反向除 10.0 防 sqlite 整数截断。
+详见 billing/0004_points_rescale.py 同款说明。
+"""
+from django.db import migrations, transaction
+
+RESCALE_STATEMENTS = [
+    "UPDATE accounts_teammember SET daily_credit_limit = daily_credit_limit * 10, monthly_credit_limit = monthly_credit_limit * 10, total_credit_limit = total_credit_limit * 10",
+    "UPDATE accounts_team SET monthly_credit_limit = monthly_credit_limit * 10 WHERE monthly_credit_limit > 0",
+    "UPDATE accounts_invitation SET monthly_credit_limit = monthly_credit_limit * 10",
+]
+
+REVERSE_STATEMENTS = [
+    "UPDATE accounts_teammember SET daily_credit_limit = daily_credit_limit / 10.0, monthly_credit_limit = monthly_credit_limit / 10.0, total_credit_limit = total_credit_limit / 10.0",
+    "UPDATE accounts_team SET monthly_credit_limit = monthly_credit_limit / 10.0 WHERE monthly_credit_limit > 0",
+    "UPDATE accounts_invitation SET monthly_credit_limit = monthly_credit_limit / 10.0",
+]
+
+
+def _run(statements):
+    def apply(apps, schema_editor):
+        with transaction.atomic(using=schema_editor.connection.alias):
+            with schema_editor.connection.cursor() as cursor:
+                for sql in statements:
+                    cursor.execute(sql)
+
+    return apply
+
+
+class Migration(migrations.Migration):
+    dependencies = [("accounts", "0007_team_monthly_credit_limit")]
+    operations = [migrations.RunPython(_run(RESCALE_STATEMENTS), _run(REVERSE_STATEMENTS))]

core/backend/apps/accounts/migrations/0009_team_price_multiplier.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.1.15 on 2026-07-03 07:41
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("accounts", "0008_points_rescale"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="team",
+            name="price_multiplier",
+            field=models.DecimalField(decimal_places=2, default=1, max_digits=5),
+        ),
+    ]