feat(customers): add initial admin bootstrap and csv import

backend/hermes/app/schemas/customer_import.py

@@ -0,0 +1,49 @@
+from typing import Literal
+
+from pydantic import BaseModel, Field
+
+ImportMode = Literal["create_only", "update_existing", "upsert"]
+ImportAction = Literal["create", "update", "skip", "error"]
+
+
+class CustomerImportIssue(BaseModel):
+    row: int
+    field: str = ""
+    message: str
+
+
+class CustomerImportPreviewRow(BaseModel):
+    row: int
+    customer_number: str = ""
+    company_name: str = ""
+    action: ImportAction
+    errors: list[CustomerImportIssue] = Field(default_factory=list)
+    warnings: list[CustomerImportIssue] = Field(default_factory=list)
+
+
+class CustomerImportSummary(BaseModel):
+    total_rows: int
+    valid_rows: int
+    error_count: int
+    warning_count: int
+    duplicate_count: int
+    create_count: int
+    update_count: int
+    skip_count: int
+
+
+class CustomerImportPreviewResponse(BaseModel):
+    mode: ImportMode
+    summary: CustomerImportSummary
+    rows: list[CustomerImportPreviewRow]
+    errors: list[CustomerImportIssue]
+    warnings: list[CustomerImportIssue]
+    duplicates: list[CustomerImportIssue]
+
+
+class CustomerImportCommitResponse(BaseModel):
+    mode: ImportMode
+    summary: CustomerImportSummary
+    created: int
+    updated: int
+    skipped: int