Fix mod_finder and mod_footer overrides to match Joomla core contracts

mod_finder:
- Use correct language keys (MOD_FINDER_SEARCH_VALUE, JSEARCH_FILTER_SUBMIT)
- Use $app (available from module dispatcher) instead of Factory
- Load com_finder.finder script and awesomplete preset
- Add show_label, show_button, show_advanced support from core
- Register com_finder extension assets
- Use $route from module dispatcher (not hardcoded)

mod_footer:
- Use $lineone variable from module helper (not $module->content)
- Add MOD_FOOTER_LINE2 language string output
- mod_footer generates its own content, it's not a custom HTML module

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/html/mod_footer/default.php

@@ -24,7 +24,6 @@ $headerClass = htmlspecialchars($params->get('header_class', ''), ENT_COMPAT, 'U
     <?php if ($module->showtitle) : ?>
         <<?php echo $headerTag; ?> class="mod-footer__title<?php echo $headerClass ? ' ' . $headerClass : ''; ?>"><?php echo $module->title; ?></<?php echo $headerTag; ?>>
     <?php endif; ?>
-    <div class="mod-footer__content">
-        <?php echo $module->content; ?>
-    </div>
+    <div class="mod-footer__line1"><?php echo $lineone; ?></div>
+    <div class="mod-footer__line2"><?php echo Text::_('MOD_FOOTER_LINE2'); ?></div>
 </div>