Add Atom feed support to list pages

Introduce `feed` metadata option to enable Atom feeds
Update list item structure with standardized fields
Add `$feedUrl` template variable for autodiscovery
Improve date handling with raw/processed date separation
Document feed generation in architecture and rendering docs
Update template examples to use new item structure

docs/03-reference/03-template-variables.md

@@ -211,6 +211,21 @@ MD5 hash of page-specific CSS for cache busting.
 **Optional:** Only set if `$pageCssUrl` exists  
 **Example:** See `$pageCssUrl` above
 
+### `$feedUrl`
+
+URL to the Atom feed for the current list page.
+
+**Type:** String (URL path)  
+**Optional:** Only set on list pages with `feed = true` in metadata  
+**Example:**
+```php
+<?php if (!empty($feedUrl)): ?>
+  <link rel="alternate" type="application/atom+xml" title="<?= htmlspecialchars($pageTitle ?? 'Feed') ?>" href="<?= htmlspecialchars($feedUrl) ?>">
+<?php endif; ?>
+```
+
+**Source:** Set when `feed = true` in the list directory's `metadata.ini`
+
 ## Page Template Variables
 
 Available in `page.php`:
@@ -238,7 +253,6 @@ All metadata for the current page.
   'title' => 'Page Title',
   'summary' => 'Short description',
   'date' => '2024-12-15',
-  'formatted_date' => '15. desember 2024',
   'show_date' => true,
   'author' => 'Jane Doe',  // Custom fields
   'tags' => 'web,design',
@@ -254,7 +268,7 @@ All metadata for the current page.
 
 <?php if (isset($metadata['date']) && ($metadata['show_date'] ?? true)): ?>
   <time datetime="<?= $metadata['date'] ?>">
-    <?= $metadata['formatted_date'] ?? $metadata['date'] ?>
+    <?= $metadata['date'] ?>
   </time>
 <?php endif; ?>
 ```
@@ -289,16 +303,15 @@ Array of items to display in the list.
 ```php
 [
   [
-    'url' => '/blog/my-post/',
-    'path' => '/content/blog/2024-12-15-my-post',
     'title' => 'My Post',
+    'url' => '/blog/my-post/',
+    'date' => '15. desember 2024',       // Formatted for display
+    'rawDate' => '2024-12-15',           // ISO YYYY-MM-DD
     'summary' => 'Short description',
-    'date' => '2024-12-15',
-    'formatted_date' => '15. desember 2024',
-    'cover_image' => '/blog/my-post/cover.jpg',
-    // All custom metadata fields...
-    'author' => 'Jane Doe',
-    'category' => 'Tutorial',
+    'cover' => '/blog/2024-12-15-my-post/cover.jpg',
+    'pdf' => null,
+    'redirect' => null,
+    'dirPath' => '/path/to/content/blog/2024-12-15-my-post',
   ],
   // ... more items
 ]
@@ -308,8 +321,8 @@ Array of items to display in the list.
 ```php
 <?php foreach ($items as $item): ?>
   <article>
-    <?php if (isset($item['cover_image'])): ?>
-      <img src="<?= $item['cover_image'] ?>" 
+    <?php if ($item['cover']): ?>
+      <img src="<?= $item['cover'] ?>" 
            alt="<?= htmlspecialchars($item['title']) ?>">
     <?php endif; ?>
     
@@ -319,13 +332,13 @@ Array of items to display in the list.
       </a>
     </h2>
     
-    <?php if (isset($item['date'])): ?>
-      <time datetime="<?= $item['date'] ?>">
-        <?= $item['formatted_date'] ?? $item['date'] ?>
+    <?php if ($item['date']): ?>
+      <time datetime="<?= $item['rawDate'] ?>">
+        <?= $item['date'] ?>
       </time>
     <?php endif; ?>
     
-    <?php if (isset($item['summary'])): ?>
+    <?php if ($item['summary']): ?>
       <p><?= htmlspecialchars($item['summary']) ?></p>
     <?php endif; ?>
   </article>
@@ -351,14 +364,15 @@ Each item in `$items` has these properties:
 
 | Property | Type | Description | Optional |
 |----------|------|-------------|----------|
-| `url` | String | Full URL to the item | No |
-| `path` | String | Filesystem path to item | No |
-| `title` | String | Item title | No |
-| `summary` | String | Short description | Yes |
-| `date` | String | ISO date (YYYY-MM-DD) | Yes |
-| `formatted_date` | String | Localized date string | Yes |
-| `cover_image` | String | URL to cover image | Yes |
-| Custom fields | Mixed | Any metadata fields | Yes |
+| `title` | String | Item title (from metadata, heading, or folder name) | No |
+| `url` | String | Full URL to the item (with trailing slash + lang prefix) | No |
+| `date` | String | Formatted date string (plugin-processed for display) | Yes |
+| `rawDate` | String | ISO date (YYYY-MM-DD) for feeds and `<time>` elements | Yes |
+| `summary` | String | Short description from metadata | Yes |
+| `cover` | String | URL to cover image | Yes |
+| `pdf` | String | URL to first PDF file | Yes |
+| `redirect` | String | External redirect URL | Yes |
+| `dirPath` | String | Filesystem path to item directory (internal use) | No |
 
 ## Adding Custom Variables
 
@@ -401,6 +415,7 @@ Then use in templates:
 | `$translations` | ✓ | — | — |
 | `$pageCssUrl` | ✓ | — | — |
 | `$pageCssHash` | ✓ | — | — |
+| `$feedUrl` | ✓ | — | — |
 | `$metadata` | — | ✓ | ✓ |
 | `$pageContent` | — | — | ✓ |
 | `$items` | — | — | ✓ |