fix: FQDN resolution and display_name blank bug; fix: Arch/Alpine/RPM packages

Bug fixes:
- get_fqdn() now prioritizes 'hostname -f' (returns full FQDN) over /etc/hostname (returns short hostname)
- Added get_hostname() for short hostname extraction
- Added hostname field to EnrollmentRequest for manager display_name population
- Updated SPEC.md and API_DOCUMENTATION.md

Package fixes:
- Arch: Added linux-patch-api.install with post_install/upgrade/remove hooks, user creation, directory creation, config handling
- Alpine: Added linux-patch-api.apk-install with pre/post install/deinstall hooks, user creation, directory creation, config handling, missing config.yaml.example
- RPM: Dynamic version from Cargo.toml, %ghost %config(noreplace) for live configs, tarball exclusions, /var/log in %files

API_DOCUMENTATION.md

@@ -909,6 +909,7 @@ Enrollment endpoints enable new hosts to register with the Patch Manager and rec
 | `fqdn` | string | Yes | Fully qualified domain name of the host |
 | `ip_address` | string | Yes | Primary non-loopback IPv4 address |
 | `os_details` | object | Yes | OS metadata (free-form JSON object) |
+| `hostname` | string | No | Short hostname (without domain). Used by the manager to populate `display_name` on approval. If omitted, the manager falls back to the FQDN. |
 
 **`os_details` common fields:**
 
@@ -933,7 +934,8 @@ curl -X POST https://manager.example.com/api/v1/enroll \
       "version_id": "12",
       "kernel": "6.1.0-kali9-amd64",
       "id_like": "debian"
-    }
+    },
+    "hostname": "host-01"
   }'
 ```