Fix: pdf chunking / table rotation (#12981)

### What problem does this PR solve?

Fix: PDF chunking issue for single-page documents
Refactor: Change the default refresh frequency to 5
Fix: Add a 0-degree threshold; require other rotation angles to exceed
it by at least 0.2
Fix: Put connector name tips to correct place
Fix: incorrect example response in delete datasets.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] Refactoring

api/apps/connector_app.py

@@ -52,7 +52,7 @@ async def set_connector():
             "source": req["source"],
             "input_type": InputType.POLL,
             "config": req["config"],
-            "refresh_freq": int(req.get("refresh_freq", 30)),
+            "refresh_freq": int(req.get("refresh_freq", 5)),
             "prune_freq": int(req.get("prune_freq", 720)),
             "timeout_secs": int(req.get("timeout_secs", 60 * 29)),
             "status": TaskStatus.SCHEDULE,