feat: add universal install script for macOS & Linux

- Add install.sh with curl one-liner installation
- Supports macOS (Homebrew), Debian/Ubuntu (apt), Fedora (dnf), Arch (pacman), Alpine (apk)
- Auto-detects OS, architecture, and Linux distro
- Checks/installs Node.js 18+, GNU Screen, warns about Claude CLI
- Clones to ~/.claudeman/app, builds, adds to PATH
- Optional systemd service setup on Linux
- Add postinstall.js for npm install verification
- Update README with simplified installation section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,13 @@
 {
   "name": "claudeman",
-  "version": "0.1370",
+  "version": "0.1375",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "claudeman",
-      "version": "0.1370",
+      "version": "0.1375",
+      "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@fastify/static": "^8.0.0",
@@ -2921,9 +2922,9 @@
       "license": "MIT"
     },
     "node_modules/lru-cache": {
-      "version": "11.2.4",
-      "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-11.2.4.tgz",
-      "integrity": "sha512-B5Y16Jr9LB9dHVkh6ZevG+vAbOsNOYCX+sXvFWFu7B3Iz5mijW3zdbMyhsh8ANd2mSWBYdJgnqi+mL7/LrOPYg==",
+      "version": "11.2.5",
+      "resolved": "https://registry.npmjs.org/lru-cache/-/lru-cache-11.2.5.tgz",
+      "integrity": "sha512-vFrFJkWtJvJnD5hg+hJvVE8Lh/TcMzKnTgCWmtBipwI5yLX/iX+5UB2tfuyODF5E7k9xEzMdYgGqaSb1c0c5Yw==",
       "license": "BlueOak-1.0.0",
       "engines": {
         "node": "20 || >=22"