Modernize integration to current Home Assistant standards

[dvejsada]

Summary

This PR implements Part A (modernization) of the review — bringing the integration in line with current Home Assistant architecture and config-flow standards. No new user-facing features are added here (that's Part B); this is a structural modernization. Behaviour is preserved, with more robust updating and config management.

Integration version bumped 2.1.0 → 3.0.0 (internal refactor; entities and unique IDs are unchanged, so existing installs upgrade in place).

What changed

A1 — DataUpdateCoordinator (new coordinator.py)

Replaces the hand-rolled hub + register_callback/publish_updates pattern. Every entity is now a CoordinatorEntity, so a single centralized poll drives all entities and availability is handled automatically. Previously the entire board stopped refreshing if the "updated" sensor was disabled (it was the only polling entity) — that fragility is gone.

A2 — entry.runtime_data

The coordinator is stored on entry.runtime_data with a typed PIDConfigEntry instead of hass.data[DOMAIN], removing ~all the # type: ignore[Any] dict lookups across the platforms.

A3 — Shared aiohttp session + manifest

• dep_board_api now uses Home Assistant's shared async_get_clientsession instead of opening a brand-new ClientSession on every request; client/timeout errors are wrapped as CannotConnect.
• manifest.json: dropped aiohttp/attrs from requirements (both ship with core), added integration_type: "device", bumped version.

A4 — Config-flow correctness

• VERSION = 1 (was the invalid float 0.1).
• Removed the deprecated and incorrect CONNECTION_CLASS.
• FlowResult → ConfigFlowResult.
• Sets a unique_id per stop and aborts on duplicates.
• The unknown-error branch now uses a real translation key instead of a raw string.

A5 — Options + reauth flows

• Options flow for the tunables (departures, calendar events, walking offset). Reads options with a fallback to data, so existing entries keep working with no migration; the entry reloads on change.
• Reauth flow: the coordinator raises ConfigEntryAuthFailed on an invalid key, so an expired key can be replaced via the standard re-auth prompt instead of deleting and re-adding the board.

A6 — Smaller standards fixes

• homeassistant.util.dt.now() instead of a hardcoded ZoneInfo("Europe/Prague").
• Infotext binary-sensor icon now derives from is_on (was reading the wrong attribute).
• Typed system_health_info.
• Added strings.json (source of truth) and extended all translations (en/cs/de/sk) with the new options/reauth/unknown/already_configured keys. Also fixed a pre-existing cs.json key typo (cal_events_count → cal_events_number).

Testing

• python -m py_compile passes on all modules.
• pyflakes is clean (no unused imports / undefined names).
• Home Assistant requires Python 3.13, which isn't available in this environment, so a full runtime/hassfest run wasn't possible locally — hassfest runs in CI. HA API usage was reviewed against current APIs (coordinator config_entry= kwarg, runtime_data, ConfigFlowResult, async_update_reload_and_abort, async_get_options_flow).

🤖 Generated with Claude Code

https://claude.ai/code/session_01Ww8phBs758zj4tCrato36c

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