refactor(desktop): organize lib modules by domain

apps/desktop/src/lib/database/databaseFileDetection.ts

@@ -0,0 +1,18 @@
+import * as api from "@/lib/backend/api";
+
+export const SQLITE_DATABASE_FILE_EXTENSIONS = ["db", "db3", "sqlite", "sqlite3", "sqlitedb"];
+
+const SQLITE_DATABASE_EXTENSION_SET = new Set(SQLITE_DATABASE_FILE_EXTENSIONS.map((extension) => `.${extension}`));
+
+export function databaseTypeFromKnownExtension(path: string): "sqlite" | "duckdb" | null {
+  const lower = path.toLowerCase();
+  if (lower.endsWith(".duckdb")) return "duckdb";
+  if ([...SQLITE_DATABASE_EXTENSION_SET].some((extension) => lower.endsWith(extension))) return "sqlite";
+  return null;
+}
+
+export async function detectDatabaseFileType(path: string): Promise<"sqlite" | "duckdb" | null> {
+  const knownType = databaseTypeFromKnownExtension(path);
+  if (knownType) return knownType;
+  return (await api.isSqliteDatabaseFile(path).catch(() => false)) ? "sqlite" : null;
+}