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.

bambu_run/migrations/0008_printermetrics_nozzle_info.py

@@ -0,0 +1,22 @@
+# Generated by Django 5.2.8 on 2026-06-20 14:22
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("bambu_run", "0007_hotend_hotendsnapshot"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="printermetrics",
+            name="nozzle_info",
+            field=models.JSONField(
+                blank=True,
+                default=list,
+                help_text="Parsed per-poll nozzle/hotend info list",
+            ),
+        ),
+    ]