feat(ai): 自由创作视频生成全量移植(/free-create)——Seedance 文/图生视频+按时长计费+人物素材库

后端:
- free_video.py: 提交/轮询/收藏/软删全链路,复用 AITask(新增 is_deleted/is_favorited, migration 0022)
- video_pricing.py: 按时长 token 计费(×1.10 buffer+clamp); video_errors.py 错误归一; media_probe.py 时长探测
- catalog/volcano: Seedance free-video 模型接入+seed(migration 0023)
- 素材库: FreeAssetGroup/FreeAsset(火山 Assets API 引用登记, migration 0009)+ 上传/轮询/删除接口
- settings: FREE_VIDEO_MAX_CONCURRENT 团队并发闸(默认3); CELERY_TASK_ALWAYS_EAGER 本地联调开关(生产恒关)
- 测试: test_free_video.py 新增; billing/products/projects tests 配套调整

前端:
- /free-create 页面+components/free-create/ 全套(输入栏/@mention 素材引用/生成卡/视频详情弹窗/素材库弹窗)
- api.ts/types.ts 扩展 free-video 与 free-assets 接口; 路由/侧边栏入口接入

bug/: 测试清单 (11)(12) 与截图归档

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

core/backend/apps/assets/migrations/0009_freeassetgroup_freeasset_and_more.py

@@ -0,0 +1,135 @@
+# Generated by Django 5.1.15 on 2026-07-02 07:23
+
+import django.db.models.deletion
+import uuid
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("accounts", "0007_team_monthly_credit_limit"),
+        ("assets", "0008_backfill_workbench_in_library"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="FreeAssetGroup",
+            fields=[
+                (
+                    "id",
+                    models.UUIDField(
+                        default=uuid.uuid4,
+                        editable=False,
+                        primary_key=True,
+                        serialize=False,
+                    ),
+                ),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                ("updated_at", models.DateTimeField(auto_now=True)),
+                ("name", models.CharField(max_length=128)),
+                ("description", models.TextField(blank=True)),
+                ("remote_group_id", models.CharField(max_length=128)),
+                ("thumbnail_url", models.URLField(blank=True)),
+                ("is_deleted", models.BooleanField(default=False)),
+                (
+                    "created_by",
+                    models.ForeignKey(
+                        blank=True,
+                        null=True,
+                        on_delete=django.db.models.deletion.SET_NULL,
+                        related_name="created_%(class)s_set",
+                        to=settings.AUTH_USER_MODEL,
+                    ),
+                ),
+                (
+                    "team",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="%(class)s_set",
+                        to="accounts.team",
+                    ),
+                ),
+            ],
+            options={
+                "ordering": ["-created_at"],
+            },
+        ),
+        migrations.CreateModel(
+            name="FreeAsset",
+            fields=[
+                (
+                    "id",
+                    models.UUIDField(
+                        default=uuid.uuid4,
+                        editable=False,
+                        primary_key=True,
+                        serialize=False,
+                    ),
+                ),
+                ("created_at", models.DateTimeField(auto_now_add=True)),
+                ("updated_at", models.DateTimeField(auto_now=True)),
+                ("remote_asset_id", models.CharField(max_length=128)),
+                ("name", models.CharField(blank=True, max_length=128)),
+                ("url", models.URLField(blank=True, max_length=1024)),
+                (
+                    "asset_type",
+                    models.CharField(
+                        choices=[
+                            ("Image", "Image"),
+                            ("Video", "Video"),
+                            ("Audio", "Audio"),
+                        ],
+                        default="Image",
+                        max_length=16,
+                    ),
+                ),
+                ("thumbnail_url", models.URLField(blank=True, max_length=1024)),
+                ("duration", models.FloatField(blank=True, null=True)),
+                (
+                    "status",
+                    models.CharField(
+                        choices=[
+                            ("processing", "Processing"),
+                            ("active", "Active"),
+                            ("failed", "Failed"),
+                        ],
+                        default="processing",
+                        max_length=16,
+                    ),
+                ),
+                ("error_message", models.TextField(blank=True)),
+                (
+                    "group",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE,
+                        related_name="assets",
+                        to="assets.freeassetgroup",
+                    ),
+                ),
+            ],
+            options={
+                "ordering": ["-created_at"],
+            },
+        ),
+        migrations.AddIndex(
+            model_name="freeassetgroup",
+            index=models.Index(
+                fields=["team", "-created_at"], name="assets_free_team_id_c0cbb2_idx"
+            ),
+        ),
+        migrations.AddIndex(
+            model_name="freeasset",
+            index=models.Index(
+                fields=["group", "-created_at"], name="assets_free_group_i_b2a9ec_idx"
+            ),
+        ),
+        migrations.AddIndex(
+            model_name="freeasset",
+            index=models.Index(
+                fields=["remote_asset_id"], name="assets_free_remote__49909d_idx"
+            ),
+        ),
+    ]