feat: include atm-tui in NixOS ATM deployments

Add atm-tui as a flake input and include it in environment.systemPackages
for both live and installed NixOS configs. The TUI will be available as
'atm-tui' on PATH after deployment — no more manual SCP.

The binary is pushed to cachix alongside the ATM app, so douro pulls
it from the binary cache on upgrade (no local compilation needed).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

flake.lock

@@ -1,5 +1,25 @@
 {
   "nodes": {
+    "atm-tui": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs-unstable"
+        ]
+      },
+      "locked": {
+        "lastModified": 1774249805,
+        "narHash": "sha256-NLRIrb6fLYx9qkIMX+5yOLQdLTkXKAeeEaKrk96sYvw=",
+        "ref": "refs/heads/main",
+        "rev": "e28ba583d95597ad0b79c307dca8b19cb1d601c3",
+        "revCount": 20,
+        "type": "git",
+        "url": "ssh://forgejo@git.atitlan.io/aiolabs/atm-tui.git"
+      },
+      "original": {
+        "type": "git",
+        "url": "ssh://forgejo@git.atitlan.io/aiolabs/atm-tui.git"
+      }
+    },
     "cachix": {
       "inputs": {
         "devenv": [
@@ -479,6 +499,7 @@
     },
     "root": {
       "inputs": {
+        "atm-tui": "atm-tui",
         "determinate": "determinate",
         "devenv": "devenv",
         "flake-utils": "flake-utils",