Update CLI tools to use valkey-glide

## Objective

Update CLI tools to use valkey-glide instead of redis-py for Redis operations.

## Files to modify

- `src/ai/backend/manager/cli/redis.py`
- Line 8: Import statements
- Lines 29-31, 46: Redis ping and debugging functionality
- `src/ai/backend/manager/cli/scheduler.py` (lines 11-13)
- `src/ai/backend/manager/cli/__main__.py` (lines 245-246)
- `src/ai/backend/appproxy/common/utils.py` (line 25)

## Tasks

- [ ] Replace redis-py imports with valkey-glide
- [ ] Update Redis client instantiation in CLI commands
- [ ] Update exception handling for valkey-glide
- [ ] Test CLI commands (redis ping, scheduler commands, etc.)

## Related

Part of BA-2585 - Retire redis-py entirely

JIRA Issue: BA-3271