npins: enhance import-from-flake capabilities

We still chose this implementation because `getFlake' is "broken".
c.f. https://github.com/andir/npins/issues/159#issuecomment-3201185411

Also this avoids the double fetch problem.
c.f. https://github.com/andir/npins/issues/159#issuecomment-3148532945

npins/sources.json

@@ -75,6 +75,23 @@
       "url": null,
       "hash": "07d2mzjnggbxlpqarcj65xdndkqxcab38lkbbqh65cyfqzqahdg0"
     },
+    "flake-compat": {
+      "type": "GitRelease",
+      "repository": {
+        "type": "GitHub",
+        "owner": "edolstra",
+        "repo": "flake-compat"
+      },
+      "pre_releases": false,
+      "version_upper_bound": null,
+      "release_prefix": null,
+      "submodules": false,
+      "version": "v1.1.0",
+      "revision": "ff81ac966bb2cae68946d5ed5fc4994f96d0ffec",
+      "url": "https://api.github.com/repos/edolstra/flake-compat/tarball/v1.1.0",
+      "hash": "19d2z6xsvpxm184m41qrpi1bplilwipgnzv9jy17fgw421785q1m",
+      "frozen": true
+    },
     "home-manager": {
       "type": "Git",
       "repository": {