feat(v5.10.0): v5.4.0 + v5.5.0 features — backlinks, page/collection duplication, trash purge, version history, markdown import, embed/bookmark/video/audio blocks, cover & icon, OG metadata

- Migration v7: page_versions table + pages.cover_url/page_icon columns
- Trash service (purge_expired 30-day) + daily scheduler
- Board API: duplicate page, backlinks, versions (snapshot/list/restore), cover/icon upload, markdown/file import
- Collections API: duplicate collection (deep copy properties/views/pages/data sources)
- Export service: render embed/bookmark/video/audio in markdown/HTML/PDF/public
- Public page renderer: cover image + icon
- Editor: slash commands for media blocks, lightbox, version history UI, backlinks panel, cover/icon picker, import modal
- OG metadata endpoint for bookmark cards
- 386 tests passing

app/migrations.py

@@ -300,6 +300,41 @@ def _migration_v520_security_projects(conn: sqlite3.Connection) -> None:
         )
 
 
+@register(7, "v5.4.0/v5.5.0: page versions, cover + icon")
+def _migration_v54_page_versions_cover(conn: sqlite3.Connection) -> None:
+    """v5.4.0 (version history + page duplication) & v5.5.0 (cover & icon).
+
+    ``page_versions``  — undoable version snapshots for block-editor pages
+                         (NOT tied to ``collection_pages`` like the legacy
+                         ``page_history`` table). One row per save with the
+                         full block list + title so the UI can browse/restore.
+    ``pages.cover_url`` — image cover shown above the page title.
+    ``pages.page_icon`` — emoji / icon label shown next to the title.
+    """
+    conn.execute(
+        """
+        CREATE TABLE IF NOT EXISTS page_versions (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            page_id INTEGER NOT NULL REFERENCES pages(id) ON DELETE CASCADE,
+            user_id INTEGER REFERENCES users(id),
+            title TEXT NOT NULL DEFAULT '',
+            blocks_json TEXT NOT NULL DEFAULT '[]',
+            note TEXT NOT NULL DEFAULT '',
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+        )
+        """
+    )
+    conn.execute(
+        "CREATE INDEX IF NOT EXISTS idx_page_versions_page ON page_versions(page_id, created_at)"
+    )
+
+    _pcols = {r[1] for r in conn.execute("PRAGMA table_info(pages)").fetchall()}
+    if "cover_url" not in _pcols:
+        conn.execute("ALTER TABLE pages ADD COLUMN cover_url TEXT DEFAULT ''")
+    if "page_icon" not in _pcols:
+        conn.execute("ALTER TABLE pages ADD COLUMN page_icon TEXT DEFAULT ''")
+
+
 @register(4, "database templates (icon) + property validation")
 def _migration_db_templates_validation(conn: sqlite3.Connection) -> None:
     """v5.3.0: database templates get an icon, properties a validation config,