Add versioned DB migrations, startup error dialog and native basics

rusqlite_migration with a VACUUM INTO backup before upgrading; M2 adds GST
registration, snapshot, cancellation and draft columns and backfills
snapshots for existing invoices. Startup failures now show a native dialog
instead of exiting silently. Adds single-instance and window-state plugins,
minimum window 960x600, embedBootstrapper, DMABUF workaround on Linux and
xbps dependency updates.

src/lib/types.ts

@@ -19,6 +19,10 @@ export interface Settings {
   currency: string;
   onboarded: boolean;
   theme: string;
+  gstRegistration: string;
+  defaultHsnSac: string;
+  signatoryName: string;
+  signatoryDesignation: string;
 }
 
 export interface BankAccount {

src/pdf/InvoiceDocument.test.tsx

@@ -33,6 +33,10 @@ const vendor: Settings = {
   currency: "INR",
   onboarded: true,
   theme: "g10",
+  gstRegistration: "unregistered",
+  defaultHsnSac: "",
+  signatoryName: "",
+  signatoryDesignation: "",
 };
 
 const bank: BankAccount = {