feat: public text items, wall, and detail API

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/schemas.py

@@ -0,0 +1,39 @@
+from datetime import datetime
+from typing import Literal
+
+from pydantic import BaseModel, Field
+
+
+TTLOption = Literal["1h", "24h", "7d", "never"]
+
+
+class ItemCreate(BaseModel):
+    body: str = Field(min_length=1)
+    title: str | None = None
+    is_public: bool = True
+    burn_after_read: bool = False
+    ttl: TTLOption = "24h"
+
+
+class ItemOut(BaseModel):
+    slug: str
+    kind: str
+    title: str
+    body: str | None = None
+    file_name: str | None = None
+    mime: str | None = None
+    size_bytes: int | None = None
+    is_public: bool
+    burn_after_read: bool
+    expires_at: datetime | None
+    created_at: datetime
+    view_count: int
+
+    model_config = {"from_attributes": True}
+
+
+class WallResponse(BaseModel):
+    items: list[ItemOut]
+    page: int
+    page_size: int
+    total: int