feat(backup): add enterprise backup & restore foundation

backend/hermes/app/schemas/backup.py

@@ -0,0 +1,57 @@
+from datetime import datetime
+
+from pydantic import BaseModel, Field
+
+
+class BackupManifest(BaseModel):
+    backup_id: str
+    created_at: datetime
+    app_version: str
+    backup_type: str = "full"
+    database_url_host_anonymized: str
+    database_name: str
+    storage_base_path: str
+    included_sections: list[str] = Field(default_factory=list)
+    file_count: int = 0
+    total_size_bytes: int = 0
+    checksum_sha256: str
+    created_by_user_id: int | None = None
+    created_by_username: str = ""
+
+
+class BackupSummary(BaseModel):
+    filename: str
+    size_bytes: int
+    created_at: datetime | None = None
+    app_version: str = ""
+    backup_type: str = "full"
+    database_name: str = ""
+    storage_base_path: str = ""
+    file_count: int = 0
+    total_size_bytes: int = 0
+    created_by_user_id: int | None = None
+    created_by_username: str = ""
+    validation_status: str = "valid"
+    validation_message: str = ""
+
+
+class BackupListResponse(BaseModel):
+    items: list[BackupSummary] = Field(default_factory=list)
+    total_count: int = 0
+    total_size_bytes: int = 0
+    latest_backup_at: datetime | None = None
+
+
+class BackupValidationResponse(BaseModel):
+    filename: str
+    valid: bool
+    message: str
+    issues: list[str] = Field(default_factory=list)
+    checksum_valid: bool = False
+    restore_supported: bool = False
+    requires_cli_restore: bool = True
+    manifest: BackupManifest | None = None
+
+
+class BackupRestoreRequest(BaseModel):
+    confirm_text: str