Add support for Nix and NixOS (#130)

* fix: add missing resolved/integrity fields to package-lock.json

npm omits resolved URLs and integrity hashes for workspace-local
node_modules overrides. This breaks offline installers like Nix's
npm ci. Add the missing fields for 25 workspace-hoisted packages.

* feat: add Nix flake with package and NixOS module

Add a Nix flake that builds the Paseo daemon (server + CLI) and
provides a NixOS module for declarative deployment.

Package (nix/package.nix):
- Builds relay, server, and CLI workspaces
- Skips onnxruntime-node install script (sandbox-incompatible)
- Rebuilds only node-pty for native terminal support
- Source filter excludes app/website/desktop workspaces

NixOS module (nix/module.nix):
- Systemd service with configurable user, port, listen address
- allowedHosts for DNS rebinding protection
- relay.enable to toggle remote access via app.paseo.sh
- inheritUserEnvironment to expose user tools (git, ssh) to agents
- openFirewall and extra environment variables

ci: add Nix hash maintenance scripts and workflows

scripts/fix-lockfile.mjs:
  Adds missing resolved/integrity fields to package-lock.json for
  workspace-local overrides. Idempotent, uses `npm view`.

scripts/update-nix.sh:
  Runs fix-lockfile.mjs, prefetches deps, computes NAR hash, and
  updates npmDepsHash in nix/package.nix. Supports --check for CI.

.github/workflows/nix-build.yml:
  Builds the Nix package on push/PR and verifies the lockfile and
  hash are up to date.

.github/workflows/fix-nix-hash.yml:
  Auto-fixes lockfile signatures and Nix hash on dependabot PRs.

fix: update npmDepsHash after upstream sync

nix: allowlist workspace symlinks instead of blocklist

Prevents build failures when upstream adds new workspace packages.

* don't block PRs on nix failures

* better document npm workaround

* fix hash update script, and update hash

* integrate with npm run build:daemon

* ci: trigger nix build on highlight changes

* fix(nix): update npmDepsHash

---------

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1772963539,
+        "narHash": "sha256-9jVDGZnvCckTGdYT53d/EfznygLskyLQXYwJLKMPsZs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9dcb002ca1690658be4a04645215baea8b95f31d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}