feat(core): add sequence schemas

app/schemas/sequence.py

@@ -0,0 +1,32 @@
+"""Sequence schemas — create, update, read, list."""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field
+
+
+class SequenceCreate(BaseModel):
+    name: str = Field(..., min_length=1, max_length=100, description="e.g. invoice, quote")
+    prefix: str = Field("", max_length=20, description="e.g. RE-2026-")
+    padding: int = Field(4, ge=1, le=10, description="Zero-pad width, e.g. 4 -> 0001")
+
+
+class SequenceUpdate(BaseModel):
+    name: str | None = Field(None, min_length=1, max_length=100)
+    prefix: str | None = Field(None, max_length=20)
+    padding: int | None = Field(None, ge=1, le=10)
+
+
+class SequenceResponse(BaseModel):
+    id: str
+    name: str
+    prefix: str
+    next_number: int
+    padding: int
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class SequenceListResponse(BaseModel):
+    items: list[SequenceResponse]
+    total: int