feat(12-02): wire all template strings to Alpine i18n store

- dashboard.html: headings, quick actions, empty states wired to x-text
- printers.html: h1, add button, h2 wired to x-text
- printers_new.html: all form labels (span pattern), options, submit buttons wired
- clients.html: headings, label, submit button wired
- client_detail.html: back link, section heading wired
- drivers.html: all headings, label, buttons, spinner wired
- packages.html: heading, description, table headers, empty state wired
- printer_detail.html: all dt/dd, section headings, copy buttons, script/export links wired with conditional Jinja2 for color/collate/client
- partials/printer_list.html: table headers, Yes/No cells (Alpine ternary), delete button wired
- partials/printer_edit_modal.html: edit trigger, modal title, all labels (span pattern), options, save/cancel wired
- partials/client_list.html: empty state, table headers wired
- partials/driver_list.html: table headers, unknown values, empty state wired
- Fix test_printers_library_no_form: check form element attribute instead of UI label string (now in i18n dict)

imptune/templates/partials/client_list.html

@@ -1,12 +1,12 @@
 <div id="client-list">
   {% if not clients %}
-  <p>No clients configured yet.</p>
+  <p x-data x-text="$store.i18n.t('no_clients')">No clients configured yet.</p>
   {% else %}
   <table>
     <thead>
       <tr>
-        <th>Name</th>
-        <th>Created</th>
+        <th x-data x-text="$store.i18n.t('th_name')">Name</th>
+        <th x-data x-text="$store.i18n.t('created')">Created</th>
       </tr>
     </thead>
     <tbody>