ENHANCEMENT:Weaviate client connects and disconnects causing latency issues

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

## 📌 Issue Overview
The Weaviate backend client repeatedly connects and disconnects on every database operation instead of reusing a persistent connection, causing unnecessary performance overhead.

## 🔍 Root Cause
- `get_weaviate_client()` calls `await client.connect()` on entry and `await client.close()` on exit
- All Weaviate operations use `async with get_weaviate_client()`, triggering a full connect/disconnect cycle per request
- This occurs despite having a global client instance

## 🚨 Actual Behavior
- A new connection is established for **every** operation
- The connection is closed immediately after use
- No connection pooling or reuse
- Adds ~10–50ms latency per query
- Wastes resources and becomes a scalability bottleneck under load

```python
@asynccontextmanager
async def get_weaviate_client():
client = get_client()
try:
await client.connect() # connects every time
yield client
finally:
await client.close() # disconnects every time
```
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- [x] I want to work on this issue