feat(nvim): setup for ipynb dev work

Setup:
- molten (run python code)
- otter (lsp in markdown codeblocks)
- jupytext (convert .ipynb files to .md files transparently)
- image (display images inside neovim (e.g. matplotlib graphs))

flake.lock

@@ -260,11 +260,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1728067476,
-        "narHash": "sha256-/uJcVXuBt+VFCPQIX+4YnYrHaubJSx4HoNsJVNRgANM=",
+        "lastModified": 1727672256,
+        "narHash": "sha256-9/79hjQc9+xyH+QxeMcRsA6hDyw6Z9Eo1/oxjvwirLk=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "6e6b3dd395c3b1eb9be9f2d096383a8d05add030",
+        "rev": "1719f27dd95fd4206afb9cec9f415b539978827e",
         "type": "github"
       },
       "original": {
@@ -292,11 +292,11 @@
         "treefmt-nix": "treefmt-nix"
       },
       "locked": {
-        "lastModified": 1728145679,
-        "narHash": "sha256-qd1nr2b+WUiyzJva650LBX/3hDBru0ZSVxKHSm1BE0w=",
+        "lastModified": 1727645871,
+        "narHash": "sha256-Os3PAThU5XliKkKa+SHsFyV/EsCHogHcYONmpzb6500=",
         "owner": "nix-community",
         "repo": "nixvim",
-        "rev": "6594472fd275f6dcf5a9fba4a83d2f7fa2cf2b8a",
+        "rev": "5f4a4b47597d3b9ac26c41ff4e8da28fa662f200",
         "type": "github"
       },
       "original": {
@@ -373,11 +373,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1727984844,
-        "narHash": "sha256-xpRqITAoD8rHlXQafYZOLvUXCF6cnZkPfoq67ThN0Hc=",
+        "lastModified": 1727431250,
+        "narHash": "sha256-uGRlRT47ecicF9iLD1G3g43jn2e+b5KaMptb59LHnvM=",
         "owner": "numtide",
         "repo": "treefmt-nix",
-        "rev": "4446c7a6fc0775df028c5a3f6727945ba8400e64",
+        "rev": "879b29ae9a0378904fbbefe0dadaed43c8905754",
         "type": "github"
       },
       "original": {
@@ -388,11 +388,11 @@
     },
     "unstable": {
       "locked": {
-        "lastModified": 1728018373,
-        "narHash": "sha256-NOiTvBbRLIOe5F6RbHaAh6++BNjsb149fGZd1T4+KBg=",
+        "lastModified": 1727634051,
+        "narHash": "sha256-S5kVU7U82LfpEukbn/ihcyNt2+EvG7Z5unsKW9H/yFA=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "bc947f541ae55e999ffdb4013441347d83b00feb",
+        "rev": "06cf0e1da4208d3766d898b7fdab6513366d45b9",
         "type": "github"
       },
       "original": {