fix: share persistence + clipboard fallback + auto-save

- DB: pages.share_mode (private/invited/anyone) + published (bool)
- API: POST /board/api/share/{id} saves share settings to DB
- view_page: passes page_share_mode + page_published to template
- page_editor: inits share state from server, auto-saves on change
- Clipboard: fallback to textarea for HTTP (navigator.clipboard blocked)
- Toast: showToast() with proper timeout clearing

app/routers/board.py

@@ -383,6 +383,24 @@ async def remove_favorite(request: Request, page_id: int):
         conn.commit()
     return {"status": "removed", "page_id": page_id}
 
+# ═══════════ Share API ═══════════
+
+@router.post("/api/share/{page_id:int}")
+async def update_share(request: Request, page_id: int):
+    """Save share settings for a page."""
+    import json
+    body = await request.json()
+    mode = body.get("mode", "private")
+    published = body.get("published", False)
+    with get_conn() as conn:
+        conn.execute(
+            "UPDATE pages SET share_mode=?, published=? WHERE id=?",
+            (mode, 1 if published else 0, page_id),
+        )
+        conn.commit()
+    return {"status": "ok", "share_mode": mode, "published": published}
+
+
 # ═══════════ Trash (must be before /{owner}/{repo} catch-all) ═══════════
 
 @router.get("/api/trash")
@@ -732,7 +750,9 @@ async def view_page(request: Request, page_id: int):
         fav = conn.execute(
             "SELECT id FROM favorites WHERE user_id=? AND page_id=?", (uid, page_id)
         ).fetchone()
-    ctx = {**sidebar, "page": page, "page_favorited": fav is not None}
+    ctx = {**sidebar, "page": page, "page_favorited": fav is not None,
+           "page_share_mode": page.get("share_mode", "private"),
+           "page_published": bool(page.get("published", 0))}
     template = env.get_template("page_editor.html")
     return template.render(**ctx)