fix(server): add --workers flag to prevent single blocking request stalling HTTP server

[r266-tech]

Summary

Fixes #464

OpenViking started uvicorn with no workers argument (defaulting to 1), which means one slow or blocking request can stall the entire HTTP server process — including lightweight probes like /health.

This PR adds a workers configuration knob so operators can run multiple uvicorn worker processes and prevent this availability issue.

Changes

openviking/server/config.py

• Add workers: int = 1 field to ServerConfig
• Load server.workers from ov.conf
• Add validation in validate_server_config: reject workers < 1 with a clear error and sys.exit(1)

openviking/server/bootstrap.py

• Add --workers N CLI argument
• When workers == 1 (default): existing behaviour unchanged, app object passed directly to uvicorn.run()
• When workers > 1: use uvicorn.run('openviking.server.app:create_app', factory=True, workers=N) so each worker process independently imports and initialises its own OpenVikingService. The config file path is propagated via the OPENVIKING_CONFIG_FILE env var already set in main()

tests/server/test_server_workers_config.py (new)

• ServerConfig defaults to workers=1
• Custom workers value stored correctly
• validate_server_config rejects workers=0 and workers=-1
• validate_server_config accepts workers=1 and workers=4
• load_server_config reads workers from config file
• load_server_config defaults workers to 1 when absent

Usage

# CLI flag
openviking-server --workers 4

# ov.conf
{
  "server": {
    "workers": 4
  }
}

Limitations

• --with-bot is not supported with --workers > 1 (warning emitted, bot proxy disabled). Bot mode requires a separate single-worker instance.
• Multiple workers each hold independent in-memory state. For local SQLite backends, concurrent writes may cause contention; a networked backend is recommended for production multi-worker deployments.

Backward Compatibility

Default is workers=1, so all existing deployments are unaffected.

[MaojiaSheng]

你测过能 work 吗？我也 vibe 过类似的版本，但有些问题

[r266-tech]

Superseded by #470 with cleaner implementation approach.