ESPHome air sensor: SCD41 + BME688 via BSEC2, API encryption + OTA password

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

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+# Gitignore settings for ESPHome
+# This is an example and may include too much for your use-case.
+# You can modify this file to suit your needs.
+/.esphome/
+/secrets.yaml
+/.venv/
+__pycache__/

airsensor-test.yaml

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+esphome:
+  name: airsensor-test
+
+esp32:
+  board: esp32-s3-devkitc-1
+  variant: esp32s3
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: !secret wifi_ssid
+  password: !secret wifi_password
+  fast_connect: true
+  reboot_timeout: 0s
+
+logger:
+  hardware_uart: UART0
+
+api:
+  encryption:
+    key: !secret api_encryption_key
+  reboot_timeout: 0s
+
+ota:
+  - platform: esphome
+    password: !secret ota_password
+
+i2c:
+  sda: GPIO8
+  scl: GPIO9
+  scan: true
+
+# BME688 via Bosch BSEC2 (IAQ / bVOC) — replaces the raw bme680 platform.
+# BSEC is Bosch closed-source; compiling it accepts their license.
+# state_save_interval keeps the learned gas baseline across reboots.
+bme68x_bsec2_i2c:
+  address: 0x76
+  model: bme688
+  operating_age: 28d
+  sample_rate: LP
+  supply_voltage: 3.3V
+  state_save_interval: 6h
+
+sensor:
+  - platform: scd4x
+    co2:
+      name: "SCD41 CO2"
+    temperature:
+      name: "SCD41 Temperature"
+    humidity:
+      name: "SCD41 Humidity"
+
+  - platform: bme68x_bsec2
+    # eCO2 intentionally omitted — real CO2 comes from the SCD41.
+    temperature:
+      name: "BME688 Temperature"
+    pressure:
+      name: "BME688 Pressure"
+    humidity:
+      name: "BME688 Humidity"
+    gas_resistance:
+      name: "BME688 Gas Resistance"
+    iaq:
+      name: "BME688 IAQ"
+    breath_voc_equivalent:
+      name: "BME688 bVOC"
+
+text_sensor:
+  - platform: bme68x_bsec2
+    iaq_accuracy:
+      name: "BME688 IAQ Accuracy"