Fix multi-interface discovery and restore manual setup option in Polish UI

[valutcizen]

This PR fixes Gree device discovery on hosts with multiple network interfaces.

Previously, discovery used a single UDP socket bound to the default route, which meant broadcast packets were effectively sent only through the default network interface. As a result, devices reachable through other interfaces or subnets were not discovered reliably.

This change updates discovery to:

• enumerate active IPv4 interfaces,
• create a dedicated broadcast socket per interface,
• send discovery packets from each interface separately,
• listen for responses across all discovery sockets,
• deduplicate devices discovered through multiple paths.

Additionally, this PR updates the Polish translation for the config flow so the initial setup screen correctly exposes both setup methods:

• automatic discovery,
• manual device setup.

Why this matters

• fixes discovery in multi-homed Home Assistant environments,
• improves support for setups with VLANs, multiple NICs, or separate LAN segments,
• restores a clear manual fallback path for Polish-speaking users.

Files changed

• custom_components/gree/gree_protocol.py
• custom_components/gree/translations/pl.json

Validation

• verified Python syntax with python3 -m py_compile
• manually reviewed config flow and translation mapping