v0.3.0b7

Pre-release for experimental active GATT concurrency testing.

Changes:

• Serialize BLE connect/disconnect per AP source as before.
• Serialize GATT read/write/notify per device, allowing different devices on the same AP to run active GATT operations concurrently.
• Add a per-source WebSocket send lock so concurrent GATT operations do not concurrently write to the same AP WebSocket.
• Add a runtime test proving two GATT reads to different devices on the same AP are sent before the first result returns.

Validation:

• 175 pytest tests passing.
• Current worktree privacy scan passed for known sensitive local values.
• Field test reported OK before release.

Note:

• This is experimental. If SwitchBot locks show timeouts or invalid-state errors, roll back to v0.3.0b6.