feat(podman): add optional Podman setup and documentation (#16273)

* feat(podman): add optional Podman setup and documentation

- Introduced `setup-podman.sh` for one-time host setup of OpenClaw in a rootless Podman environment, including user creation, image building, and launch script installation.
- Added `run-openclaw-podman.sh` for running the OpenClaw gateway as a Podman container.
- Created `openclaw.podman.env` for environment variable configuration.
- Updated documentation to include Podman installation instructions and a new dedicated Podman guide.
- Added a systemd Quadlet unit for managing the OpenClaw service as a user service.

* fix: harden Podman setup and docs (#16273) (thanks @DarwinsBuddy)

* style: format cli credentials

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

docs/docs.json

@@ -319,6 +319,10 @@
       "source": "/docker",
       "destination": "/install/docker"
     },
+    {
+      "source": "/podman",
+      "destination": "/install/podman"
+    },
     {
       "source": "/doctor",
       "destination": "/gateway/doctor"
@@ -836,7 +840,13 @@
               },
               {
                 "group": "Other install methods",
-                "pages": ["install/docker", "install/nix", "install/ansible", "install/bun"]
+                "pages": [
+                  "install/docker",
+                  "install/podman",
+                  "install/nix",
+                  "install/ansible",
+                  "install/bun"
+                ]
               },
               {
                 "group": "Maintenance",