style(templates): format Selmer .html templates for readability

Many templates were minified onto a single line. Reformatted every template under
resources/templates/ with djLint (django profile, 2-space indent) so the markup,
{% %} blocks, and {{ }} interpolations are human-readable, plus hand-split the two
multi-<span> option partials (invoice-option / rule-option). Pure reflow — no markup,
tag, or text content changed (the only content-adjacent delta is harmless trailing
whitespace inside single-interpolation elements). link.html / panel-empty.html stay on
one line (single element). resources/public/index.html left as-is (already readable,
non-template static).

Full e2e suite 72/72 green (no rendering regressions).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

resources/templates/components/a-button.html

@@ -1 +1,9 @@
-<a class="{{ classes }}"{{ attrs|safe }}>{% if indicator %}<div class="htmx-indicator flex items-center">{% include "templates/components/spinner.html" %}<div class="ml-3">Loading...</div></div>{% endif %}<div class="inline-flex gap-2 items-center justify-center{% if indicator %} htmx-indicator-hidden{% endif %}">{{ body|safe }}</div></a>
+<a class="{{ classes }}"{{ attrs|safe }}>
+  {% if indicator %}
+    <div class="htmx-indicator flex items-center">
+      {% include "templates/components/spinner.html" %}
+      <div class="ml-3">Loading...</div>
+    </div>
+  {% endif %}
+  <div class="inline-flex gap-2 items-center justify-center{% if indicator %} htmx-indicator-hidden{% endif %}">{{ body|safe }}</div>
+</a>