flake.lock: Update

Flake lock file updates:

```
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/f0946fa5f1fb876a9dc2e1850d9d3a4e3f914092' (2025-03-23)
  → 'github:nixos/nixpkgs/26d499fc9f1d567283d5d56fcf367edd815dba1d' (2025-04-12)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/1e5b653dff12029333a6546c11e108ede13052eb' (2025-03-22)
  → 'github:nixos/nixpkgs/2631b0b7abcea6e640ce31cd78ea58910d31e650' (2025-04-12)
```

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1744309437,
-        "narHash": "sha256-QZnNHM823am8apCqKSPdtnzPGTy2ZB4zIXOVoBp5+W0=",
+        "lastModified": 1744440957,
+        "narHash": "sha256-FHlSkNqFmPxPJvy+6fNLaNeWnF1lZSgqVCl/eWaJRc4=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f9ebe33a928b5d529c895202263a5ce46bdf12f7",
+        "rev": "26d499fc9f1d567283d5d56fcf367edd815dba1d",
         "type": "github"
       },
       "original": {
@@ -36,11 +36,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1744232761,
-        "narHash": "sha256-gbl9hE39nQRpZaLjhWKmEu5ejtQsgI5TWYrIVVJn30U=",
+        "lastModified": 1744463964,
+        "narHash": "sha256-LWqduOgLHCFxiTNYi3Uj5Lgz0SR+Xhw3kr/3Xd0GPTM=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f675531bc7e6657c10a18b565cfebd8aa9e24c14",
+        "rev": "2631b0b7abcea6e640ce31cd78ea58910d31e650",
         "type": "github"
       },
       "original": {