Add code field to archive content edit form and IDB

- Expose archive_content.code in edit form (trusted + edit_mode only)
- Add code to properties_to_save so it persists on every API load/save
- Add code field + index to Archive_Content Dexie interface (schema v2)
- Minor: center "Add" button rows in archive and content list components

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/ae_archives/ae_archives__archive_content.ts

@@ -299,6 +299,7 @@ export const properties_to_save = [
     'archive_id',
     'archive_content_type',
     'name',
+    'code',
     'description',
     'content_html',
     'content_json',

src/lib/ae_archives/db_archives.ts

@@ -90,6 +90,7 @@ export interface Archive_Content {
     archive_content_type: string;
 
     name: string;
+    code?: null | string;
     description?: null | string;
 
     content_html?: null | string;
@@ -168,7 +169,28 @@ export class MySubClassedDexie extends Dexie {
                 tmp_sort_1, tmp_sort_2,
                 enable, hide, priority, sort, group, notes, created_on, updated_on, [group+priority+sort+updated_on]`
         });
-
+        // v2: add code index to content table
+        this.version(2).stores({
+            archive: `
+                id, archive_id,
+                code,
+                account_id,
+                name,
+                original_datetime, original_timezone, original_location,
+                tmp_sort_1, tmp_sort_2,
+                enable, hide, priority, sort, group, notes, created_on, updated_on`,
+            content: `
+                id, archive_content_id,
+                archive_id,
+                archive_content_type,
+                name,
+                code,
+                hosted_file_id,
+                original_datetime, original_timezone, original_location,
+                [group+original_datetime],
+                tmp_sort_1, tmp_sort_2,
+                enable, hide, priority, sort, group, notes, created_on, updated_on, [group+priority+sort+updated_on]`
+        });
     }
 }