Add external model persistence foundation

src/db/schema/external-import-batches.ts

@@ -0,0 +1,43 @@
+import { blob, index, integer, sqliteTable, text } from "drizzle-orm/sqlite-core";
+import type {
+  ExternalCsvConfiguration,
+  ExternalCsvDocument,
+} from "../../external-model/csv/external-csv-contracts.js";
+import { externalImportKinds } from "../../external-model/domain/external-model-contracts.js";
+import { externalModelSources } from "./external-model-sources.js";
+import { projects } from "./projects.js";
+
+export const externalImportBatches = sqliteTable(
+  "external_import_batches",
+  {
+    id: text("id").primaryKey(),
+    projectId: text("project_id")
+      .notNull()
+      .references(() => projects.id, { onDelete: "cascade" }),
+    sourceId: text("source_id")
+      .notNull()
+      .references(() => externalModelSources.id, { onDelete: "cascade" }),
+    importKind: text("import_kind", { enum: externalImportKinds }).notNull(),
+    importedAtIso: text("imported_at_iso").notNull(),
+    fileName: text("file_name").notNull(),
+    sha256: text("sha256").notNull(),
+    appliedProjectRevision: integer("applied_project_revision").notNull(),
+    configurationSnapshot: text("configuration_snapshot", { mode: "json" })
+      .$type<ExternalCsvConfiguration>()
+      .notNull(),
+    originalBytes: blob("original_bytes", { mode: "buffer" }).notNull(),
+    document: text("document", { mode: "json" })
+      .$type<ExternalCsvDocument>()
+      .notNull(),
+  },
+  (table) => [
+    index("external_import_batches_project_revision_idx").on(
+      table.projectId,
+      table.appliedProjectRevision
+    ),
+    index("external_import_batches_source_imported_idx").on(
+      table.sourceId,
+      table.importedAtIso
+    ),
+  ]
+);