feat(tag-search): add alias support to FTS index

- Add aliases column to tags table to store comma-separated alias lists
- Update FTS schema to version 2 with searchable_text field containing tag names and aliases
- Implement schema migration to rebuild index when upgrading from old schema
- Modify search logic to match aliases and return canonical tag with matched alias info
- Update index building to include aliases in searchable text for FTS matching

This enables users to search for tag aliases (e.g., "miku") and get results for the canonical tag (e.g., "hatsune_miku") with indication of which alias was matched.

web/comfyui/autocomplete.js

@@ -841,14 +841,31 @@ class AutoComplete {
     /**
      * Render an enriched autocomplete item with category badge and post count
      * @param {HTMLElement} itemEl - The item element to populate
-     * @param {Object} itemData - The enriched item data { tag_name, category, post_count }
+     * @param {Object} itemData - The enriched item data { tag_name, category, post_count, matched_alias? }
      * @param {string} searchTerm - The current search term for highlighting
      */
     _renderEnrichedItem(itemEl, itemData, searchTerm) {
         // Create name span with highlighted match
         const nameSpan = document.createElement('span');
         nameSpan.className = 'lm-autocomplete-name';
-        nameSpan.innerHTML = this.highlightMatch(itemData.tag_name, searchTerm);
+
+        // If matched via alias, show: "tag_name ← alias" with alias highlighted
+        if (itemData.matched_alias) {
+            const tagText = document.createTextNode(itemData.tag_name + ' ');
+            nameSpan.appendChild(tagText);
+
+            const aliasSpan = document.createElement('span');
+            aliasSpan.className = 'lm-matched-alias';
+            aliasSpan.innerHTML = '← ' + this.highlightMatch(itemData.matched_alias, searchTerm);
+            aliasSpan.style.cssText = `
+                font-size: 11px;
+                color: rgba(226, 232, 240, 0.5);
+            `;
+            nameSpan.appendChild(aliasSpan);
+        } else {
+            nameSpan.innerHTML = this.highlightMatch(itemData.tag_name, searchTerm);
+        }
+
         nameSpan.style.cssText = `
             flex: 1;
             min-width: 0;