chore(deps): update flake.lock (#6142)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/70ce234' (2026-08-06)
  → 'github:NixOS/nixpkgs/8be7bd0' (2026-08-14)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/6df7076' (2026-08-09)
  → 'github:oxalica/rust-overlay/b211ead' (2026-08-16)

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1785975029,
-        "narHash": "sha256-X44cn5rzytELc3NNoQsh0aLkjWA/QzPfc6HPQmsG3sU=",
+        "lastModified": 1786719841,
+        "narHash": "sha256-QcpQOT0NQEFkI77t+YXPZqDJc35iIodG7zinieOwFUg=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "70ce234312134a463ba7728e94da2486a1d237ac",
+        "rev": "8be7bd0c83f12e2e3bbba07c9044d6fed9e66f7f",
         "type": "github"
       },
       "original": {
@@ -29,11 +29,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1786247265,
-        "narHash": "sha256-cVTcTqAhzSNMOVddtBhFpuv+Vx6/SgrhgZWJiI61H24=",
+        "lastModified": 1786849542,
+        "narHash": "sha256-MS8cOa/ii1+QA8R3JWVzqEIoXimu9n50GwQDiBVTFOM=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "6df7076ea0f5697e3242719a4c71211f00411cf5",
+        "rev": "b211eadeba8b180da9453ec3413a8a3535c85b3f",
         "type": "github"
       },
       "original": {