feat: add firmware versioning and device_type support (NebuleAir/ModuleAir)

- Add VERSION file (1.0.0) and changelog.json for firmware tracking
- Add device_type config param (nebuleair_pro default, backward compatible via INSERT OR IGNORE)
- Add device_type select in admin.html Protected Settings
- Add version badge and changelog modal in Updates section
- Add get_firmware_version and get_changelog PHP endpoints
- Display firmware version in update_firmware.sh after git pull

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

changelog.json

@@ -0,0 +1,21 @@
+{
+  "versions": [
+    {
+      "version": "1.0.0",
+      "date": "2026-02-11",
+      "changes": {
+        "features": [
+          "Support multi-device : NebuleAir Pro / ModuleAir Pro",
+          "Systeme de versioning firmware",
+          "Changelog viewer dans l'interface web"
+        ],
+        "improvements": [],
+        "fixes": [],
+        "compatibility": [
+          "Les capteurs existants sont automatiquement configures en 'nebuleair_pro'"
+        ]
+      },
+      "notes": "Premiere version tracee. Les capteurs anterieurs recevront device_type=nebuleair_pro par defaut lors de la mise a jour."
+    }
+  ]
+}