Add ability to switch between organisations without signing out (#564)

This adds a 'Change' link in the account section of the header, for
those users who have an account at more than one organisation:

<img width="987" height="149" alt="Screenshot 2025-12-02 at 23 32 00"
src="https://github.com/user-attachments/assets/8921c93b-7bde-47b3-a188-c9fd48e4a57c"
/>

The change link takes them back to a screen where they can select an
organisation.

<img width="795" height="369" alt="Screenshot 2025-12-02 at 23 32 45"
src="https://github.com/user-attachments/assets/8b98c2df-d746-4f1a-8ee9-c2c6b8c24e27"
/>

This avoids the need to have to log out and log back in again.

Author: frankieroberto

app/views/includes/header.html

@@ -102,6 +102,13 @@
 
 {% endif %}
 
+{% set organisationHtml %}
+  {{ currentOrganisation.name | truncate(30) }}
+  {% if currentUser and currentOrganisation and ((currentUser.organisations | length) > 1) %}
+    <a href="/auth/select-organisation" class="nhsuk-link--reverse">Change<span class="nhsuk-u-visually-hidden"> organisation</span></a>
+  {% endif %}
+{% endset %}
+
 {{ header({
   service: {
     text: "Record a vaccination",
@@ -115,7 +122,7 @@
         icon: true
       } if currentUser,
       {
-        text: (currentOrganisation.name | truncate(30))
+        html: organisationHtml
       } if currentOrganisation,
       {
         href: '/sign-out',

app/views/user-profile/index.html

@@ -25,7 +25,7 @@ <h1 class="nhsuk-heading-l">Your profile</h1>
         {% endset %}
 
         {% set organisationHtml %}
-          <div>{{ currentOrganisation.name }}</div>
+          <div>{{ currentOrganisation.name }} ({{ currentOrganisation.id }})</div>
           {% if currentOrganisation.type != "Region" %}
             <p class="app-summary__explanation">
               {{ currentOrganisation.address.line1 }}, {{ currentOrganisation.address.postcode }}