feat: v5.14.0 Synced blocks - block created once, edited everywhere

- Table synced_blocks (source of truth) + page_synced_blocks (references)
- Migration 15 + service app/services/synced_blocks.py
- API endpoints: CRUD synced blocks, add/remove page references
- Editor: /synced slash command, synced block rendering with badge
- Realtime: _propagate_synced broadcasts updates to all referencing rooms
- Export: synced blocks resolved in Markdown/HTML/PDF
- 18 tests in tests/test_v514_synced_blocks.py

Co-authored-by: FlowDeck <[email protected]>

app/services/export.py

@@ -529,6 +529,20 @@ def blocks_to_markdown(blocks: list) -> str:
                 out.append(f"[{url}]({url})" if url else "[embed]")
         elif t == "table":
             out.append(_table_to_markdown(b))
+        elif t == "synced":
+            synced_id = b.get("synced_id")
+            if synced_id:
+                try:
+                    from app.services.synced_blocks import get_synced_block
+                    sb = get_synced_block(synced_id)
+                    if sb and sb.get("content"):
+                        resolved = json.loads(sb["content"])
+                        if isinstance(resolved, list):
+                            out.append(blocks_to_markdown(resolved))
+                        else:
+                            out.append(str(resolved))
+                except Exception:
+                    out.append(f"[Synced block {synced_id}]")
         else:
             out.append(c)
     return "\n\n".join(filter(None, out))
@@ -678,6 +692,20 @@ def blocks_to_html(blocks: list) -> str:
                 )
         elif t == "table":
             parts.append(_table_to_html(b))
+        elif t == "synced":
+            synced_id = b.get("synced_id")
+            if synced_id:
+                try:
+                    from app.services.synced_blocks import get_synced_block
+                    sb = get_synced_block(synced_id)
+                    if sb and sb.get("content"):
+                        resolved = json.loads(sb["content"])
+                        if isinstance(resolved, list):
+                            parts.append(blocks_to_html(resolved))
+                        else:
+                            parts.append(f"<p>{_text(resolved)}</p>")
+                except Exception:
+                    parts.append(f"<p>[Synced block {synced_id}]</p>")
         else:
             parts.append(f"<p>{c}</p>")
     return "\n".join(parts)