fix(theme): improve post-grid spacing, pagination and archive templates

- Fix flexbox gap issue causing unequal horizontal/vertical spacing
- Reset Bootstrap row/col margins to use only CSS gap property
- Replace WordPress pagination with Bootstrap-style pagination
- Add cta-post component to category.php and archive.php templates
- Fix spacing controls UI with separate horizontal/vertical gap fields
- Update FieldMapper with new gap_horizontal and gap_vertical attributes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Admin/PostGrid/Infrastructure/FieldMapping/PostGridFieldMapper.php

@@ -81,7 +81,8 @@ final class PostGridFieldMapper implements FieldMapperInterface
             'postGridPaginationActiveColor' => ['group' => 'colors', 'attribute' => 'pagination_active_color'],
 
             // Spacing
-            'postGridGridGap' => ['group' => 'spacing', 'attribute' => 'grid_gap'],
+            'postGridGapHorizontal' => ['group' => 'spacing', 'attribute' => 'gap_horizontal'],
+            'postGridGapVertical' => ['group' => 'spacing', 'attribute' => 'gap_vertical'],
             'postGridCardPadding' => ['group' => 'spacing', 'attribute' => 'card_padding'],
             'postGridSectionMarginTop' => ['group' => 'spacing', 'attribute' => 'section_margin_top'],
             'postGridSectionMarginBottom' => ['group' => 'spacing', 'attribute' => 'section_margin_bottom'],