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-tauri/capabilities/default.json

@@ -6,6 +6,25 @@
   "permissions": [
     "core:default",
     "dialog:default",
-    "opener:default"
+    "opener:default",
+    "window-state:default",
+    {
+      "identifier": "opener:allow-open-path",
+      "allow": [
+        { "path": "$DOCUMENT/**" },
+        { "path": "$DOWNLOAD/**" },
+        { "path": "$DESKTOP/**" },
+        { "path": "$HOME/**" }
+      ]
+    },
+    {
+      "identifier": "opener:allow-reveal-item-in-dir",
+      "allow": [
+        { "path": "$DOCUMENT/**" },
+        { "path": "$DOWNLOAD/**" },
+        { "path": "$DESKTOP/**" },
+        { "path": "$HOME/**" }
+      ]
+    }
   ]
 }