feat: full Home Assistant integration

- PHP: _fireHaWebhook(), _sendHaNotify(), haInventorySensor(), haTestConnection()
- PHP: ha_sensor + ha_test routing actions
- PHP: getServerSettings() exposes ha_token (consistent with tts_token)
- PHP: saveSettings() handles all HA_* env keys (url, token, tts_entity, webhook_id, events, notify_service, expiry_days)
- PHP: bringAddItems(), shoppingAdd(), updateInventory() fire shopping_add / stock_update webhooks
- Cron: daily HA expiry/expired webhook + push notify with flag-file guard
- HTML: 🏠 Settings tab button + full HA panel (connection, TTS, webhook, notify, sensor cards)
- JS: serverKeys + loadSettingsUI extended with HA fields
- JS: _applyHaSettingsUI(), _loadHaTab(), _renderHaSensorYaml()
- JS: onHaEnabledChange(), testHaConnection(), applyHaTtsPreset()
- JS: saveHaSettings(), copyHaSensorYaml(), showHaWebhookHelp()
- JS: _buildHaTtsRequest() for HA media_player TTS
- JS: speakCookingStep() now supports HA TTS as first-priority path
- JS: onTtsEngineChange() fixed to show server section for both 'server' and 'custom'
- Translations: settings.ha.* (52 keys) in all 5 languages (it/en/de/fr/es)
- .env.example: HA_ENABLED/URL/TOKEN/TTS_ENTITY/WEBHOOK_ID/EVENTS/NOTIFY_SERVICE/EXPIRY_DAYS
- docs/wiki/Home-Assistant.md: new wiki page (REST sensors, webhooks, TTS, push notify, troubleshooting)
- README: HA integration highlighted as first feature block

.env.example

@@ -129,6 +129,28 @@ GDRIVE_RETENTION_DAYS=30
 # Leave empty to allow anyone with access to the server to change settings.
 SETTINGS_TOKEN=
 
+# ── Home Assistant Integration ────────────────────────────────────────────────
+# All HA settings can also be configured from the Settings → 🏠 tab.
+#
+# HA_ENABLED: master switch for all HA features (webhooks, TTS, sensors)
+HA_ENABLED=false
+# HA_URL: base URL of your HA instance — no trailing slash
+# Examples: http://homeassistant.local:8123  or  http://192.168.1.50:8123
+HA_URL=
+# HA_TOKEN: Long-Lived Access Token (HA Profile → Security → Long-Lived Access Tokens)
+HA_TOKEN=
+# HA_TTS_ENTITY: media_player entity for recipe step TTS (e.g. media_player.living_room)
+HA_TTS_ENTITY=
+# HA_WEBHOOK_ID: ID of an HA automation's Webhook trigger
+HA_WEBHOOK_ID=
+# HA_WEBHOOK_EVENTS: comma-separated events to fire webhooks for
+#   Available: expiry, shopping_add, stock_update, barcode_scan
+HA_WEBHOOK_EVENTS=expiry,shopping_add,stock_update
+# HA_NOTIFY_SERVICE: HA notify service for push alerts (e.g. notify.mobile_app_my_phone)
+HA_NOTIFY_SERVICE=
+# HA_EXPIRY_DAYS: days before expiry to trigger expiry alert (default 3)
+HA_EXPIRY_DAYS=3
+
 # ── Developer / demo ─────────────────────────────────────────────────────────
 # DEMO_MODE: when true, all write operations are blocked (for public demos)
 DEMO_MODE=false