Feature/multi printer support (#12)

* Initial implementation of multi-printer support.

* Always show device dropdown and add bambu_diagnose for multi-printer troubleshooting.

* Add multi-AMS support: per-unit snapshot/usage tracking, grouped dashboard panels with real type labels, and dual-nozzle card UX fixes. Fixes a real-world AMS info-code parsing bug found by inspecting live H2C data.

* Add Vortek hotend rack tracking: per-SN registry with slot mapping confirmed against live MQTT capture, plus a fallback for non-inductive nozzles (e.g. H2C's fixed left nozzle) shown read-only without fabricated identity. New dashboard card hides entirely on printers with no Vortek/nozzle-info data at all.

tests/settings.py

@@ -0,0 +1,40 @@
+"""Minimal Django settings for running bambu_run's pytest suite (in-memory SQLite)."""
+
+SECRET_KEY = "test-secret-key"
+
+INSTALLED_APPS = [
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "bambu_run",
+]
+
+MIDDLEWARE = [
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+]
+
+TEMPLATES = [
+    {
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+            ],
+        },
+    },
+]
+
+DATABASES = {
+    "default": {
+        "ENGINE": "django.db.backends.sqlite3",
+        "NAME": ":memory:",
+    }
+}
+
+USE_TZ = True
+DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
+
+ROOT_URLCONF = "tests.urls"