feat(assets): align local API with cloud spec

Unify response models, add missing fields, and align input schemas with
the cloud OpenAPI spec at cloud.comfy.org/openapi.

- Replace AssetSummary/AssetDetail/AssetUpdated with single Asset model
- Add is_immutable, metadata (system_metadata), prompt_id fields
- Support mime_type and preview_id in update endpoint
- Make CreateFromHashBody.name optional, add mime_type, require >=1 tag
- Add id/mime_type/preview_id to upload, relax tags to optional
- Rename total_tags → tags in tag add/remove responses
- Add GET /api/assets/tags/refine histogram endpoint
- Add DB migration for system_metadata and prompt_id columns

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/assets/api/schemas_out.py

@@ -4,16 +4,21 @@ from typing import Any
 from pydantic import BaseModel, ConfigDict, Field, field_serializer
 
 
-class AssetSummary(BaseModel):
+class Asset(BaseModel):
     id: str
     name: str
     asset_hash: str | None = None
-    size: int | None = None
+    size: int = 0
     mime_type: str | None = None
     tags: list[str] = Field(default_factory=list)
     preview_url: str | None = None
-    created_at: datetime | None = None
-    updated_at: datetime | None = None
+    preview_id: str | None = None
+    user_metadata: dict[str, Any] = Field(default_factory=dict)
+    is_immutable: bool = False
+    metadata: dict[str, Any] | None = None
+    prompt_id: str | None = None
+    created_at: datetime
+    updated_at: datetime
     last_access_time: datetime | None = None
 
     model_config = ConfigDict(from_attributes=True)
@@ -23,50 +28,16 @@ class AssetSummary(BaseModel):
         return v.isoformat() if v else None
 
 
+class AssetCreated(Asset):
+    created_new: bool
+
+
 class AssetsList(BaseModel):
-    assets: list[AssetSummary]
+    assets: list[Asset]
     total: int
     has_more: bool
 
 
-class AssetUpdated(BaseModel):
-    id: str
-    name: str
-    asset_hash: str | None = None
-    tags: list[str] = Field(default_factory=list)
-    user_metadata: dict[str, Any] = Field(default_factory=dict)
-    updated_at: datetime | None = None
-
-    model_config = ConfigDict(from_attributes=True)
-
-    @field_serializer("updated_at")
-    def _serialize_updated_at(self, v: datetime | None, _info):
-        return v.isoformat() if v else None
-
-
-class AssetDetail(BaseModel):
-    id: str
-    name: str
-    asset_hash: str | None = None
-    size: int | None = None
-    mime_type: str | None = None
-    tags: list[str] = Field(default_factory=list)
-    user_metadata: dict[str, Any] = Field(default_factory=dict)
-    preview_id: str | None = None
-    created_at: datetime | None = None
-    last_access_time: datetime | None = None
-
-    model_config = ConfigDict(from_attributes=True)
-
-    @field_serializer("created_at", "last_access_time")
-    def _serialize_datetime(self, v: datetime | None, _info):
-        return v.isoformat() if v else None
-
-
-class AssetCreated(AssetDetail):
-    created_new: bool
-
-
 class TagUsage(BaseModel):
     name: str
     count: int
@@ -83,11 +54,15 @@ class TagsAdd(BaseModel):
     model_config = ConfigDict(str_strip_whitespace=True)
     added: list[str] = Field(default_factory=list)
     already_present: list[str] = Field(default_factory=list)
-    total_tags: list[str] = Field(default_factory=list)
+    tags: list[str] = Field(default_factory=list)
 
 
 class TagsRemove(BaseModel):
     model_config = ConfigDict(str_strip_whitespace=True)
     removed: list[str] = Field(default_factory=list)
     not_present: list[str] = Field(default_factory=list)
-    total_tags: list[str] = Field(default_factory=list)
+    tags: list[str] = Field(default_factory=list)
+
+
+class TagHistogram(BaseModel):
+    tag_counts: dict[str, int]