Add ansible-managed wifi profiles for meshcore nodes

Each node now gets three NetworkManager wifi connections via a new
wifi role: dotnetwork (home), dotmobile (phone hotspot, for field
troubleshooting), and a host-specific deployed-location network.
Credentials live in a new per-repo ansible-vault (group and host
scoped), matching the pattern already used in dotnetwork.

Also updates the README's Pi imaging instructions from Bookworm to
Trixie, matching what the nodes actually run.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

ansible/roles/wifi/tasks/main.yml

@@ -0,0 +1,40 @@
+---
+- name: WiFi — dotnetwork (home)
+  community.general.nmcli:
+    type: wifi
+    conn_name: dotnetwork
+    ssid: "{{ wifi_ssid_dotnetwork }}"
+    wifi_sec:
+      key-mgmt: wpa-psk
+      psk: "{{ wifi_password_dotnetwork }}"
+    autoconnect: true
+    state: present
+  become: true
+  tags: [wifi]
+
+- name: WiFi — dotmobile (phone hotspot, field troubleshooting)
+  community.general.nmcli:
+    type: wifi
+    conn_name: dotmobile
+    ssid: "{{ wifi_ssid_dotmobile }}"
+    wifi_sec:
+      key-mgmt: wpa-psk
+      psk: "{{ wifi_password_dotmobile }}"
+    autoconnect: true
+    state: present
+  become: true
+  tags: [wifi]
+
+- name: WiFi — deployed-location network
+  community.general.nmcli:
+    type: wifi
+    conn_name: location
+    ssid: "{{ wifi_ssid_location }}"
+    wifi_sec:
+      key-mgmt: wpa-psk
+      psk: "{{ wifi_password_location }}"
+    autoconnect: true
+    state: present
+  become: true
+  when: wifi_ssid_location is defined
+  tags: [wifi]