gitea-actions: add PlatformIO CI image for Arduino-framework ESP32 builds

New opt-in job image localhost/gitea-ci-platformio:7.0.1 (pattern matches the
ESP-IDF image): PlatformIO core 6.1.19 with the espressif32@7.0.1 platform,
xtensa toolchain and Arduino framework pre-baked via a seed project so
ephemeral job containers download nothing. First consumer is
Skudak/esp32-web-interface.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ansible/roles/gitea-actions/tasks/images.yml

@@ -41,6 +41,16 @@
     XDG_RUNTIME_DIR: "/run/user/{{ gitea_runner_uid }}"
   tags: gitea-actions
 
+- name: stage PlatformIO CI Containerfile
+  become: true
+  become_user: "{{ gitea_runner_user }}"
+  ansible.builtin.template:
+    src: Containerfile.platformio.j2
+    dest: "{{ gitea_runner_home }}/ci-images/Containerfile.platformio"
+    mode: "0644"
+  register: platformio_containerfile
+  tags: gitea-actions
+
 - name: build ESP-IDF CI image ({{ gitea_ci_espidf_image }})
   become: true
   become_user: "{{ gitea_runner_user }}"
@@ -53,3 +63,16 @@
   environment:
     XDG_RUNTIME_DIR: "/run/user/{{ gitea_runner_uid }}"
   tags: gitea-actions
+
+- name: build PlatformIO CI image ({{ gitea_ci_platformio_image }})
+  become: true
+  become_user: "{{ gitea_runner_user }}"
+  containers.podman.podman_image:
+    name: "{{ gitea_ci_platformio_image }}"
+    path: "{{ gitea_runner_home }}/ci-images"
+    build:
+      file: "{{ gitea_runner_home }}/ci-images/Containerfile.platformio"
+    force: "{{ platformio_containerfile is changed }}"
+  environment:
+    XDG_RUNTIME_DIR: "/run/user/{{ gitea_runner_uid }}"
+  tags: gitea-actions