Add H2C dual-nozzle and multi-AMS-type support

Schema (migration 0004):
- PrinterMetrics: nozzle_temp_left, nozzle_target_temp_left,
  nozzle_diameter_left, nozzle_type_left (all nullable)
- Filament: ams_unit_id (nullable int), ams_type (AMS/AMS 2 Pro/AMS HT)
- AMS_INFO_TO_TYPE map and AMS_TYPE_CHOICES on models

Parser (mqtt_client.py):
- Decode bit-packed temps from device.extruder.info[] for left/right nozzle
- Emit per-nozzle fields in get_snapshot(); legacy keys mirror right side
- AMS unit type from info code per unit dict

Collector (bambu_collector.py):
- Write left-nozzle fields to PrinterMetrics
- Set ams_unit_id + ams_type on Filament records
- Fix: poll MQTTClient.connected before pushall (not BambuPrinter._connected)
- Add 5s post-pushall wait in --once mode so response arrives before collect

Views: API and dashboard include left-nozzle series; is_dual_nozzle flag
Templates: dual-nozzle cards + chart; AMS-type badge + filter on filament list
Charts: left nozzle temp chart with conditional render
Forms: fix tray_id max=3 → max=15; add ams_unit_id, ams_type fields

bambu_run/migrations/0004_h2c_dual_nozzle_and_ams_fields.py

@@ -0,0 +1,90 @@
+# Generated by Django 5.2.8 on 2026-05-07 04:16
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("bambu_run", "0003_cloud_task"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="filament",
+            name="ams_type",
+            field=models.CharField(
+                blank=True,
+                choices=[
+                    ("AMS", "AMS"),
+                    ("AMS 2 Pro", "AMS 2 Pro"),
+                    ("AMS HT", "AMS HT"),
+                ],
+                default="",
+                help_text="Type of the AMS unit this spool is loaded in (AMS / AMS 2 Pro / AMS HT)",
+                max_length=32,
+            ),
+        ),
+        migrations.AddField(
+            model_name="filament",
+            name="ams_unit_id",
+            field=models.PositiveSmallIntegerField(
+                blank=True,
+                db_index=True,
+                help_text="Which physical AMS unit this spool is loaded in (matches MQTT ams[i].id; 128 = AMS HT)",
+                null=True,
+            ),
+        ),
+        migrations.AddField(
+            model_name="printermetrics",
+            name="nozzle_diameter_left",
+            field=models.DecimalField(
+                blank=True,
+                decimal_places=2,
+                help_text="Left nozzle diameter (mm). H2C only.",
+                max_digits=3,
+                null=True,
+            ),
+        ),
+        migrations.AddField(
+            model_name="printermetrics",
+            name="nozzle_target_temp_left",
+            field=models.DecimalField(
+                blank=True,
+                decimal_places=2,
+                help_text="Left extruder target temperature (°C). H2C only.",
+                max_digits=5,
+                null=True,
+            ),
+        ),
+        migrations.AddField(
+            model_name="printermetrics",
+            name="nozzle_temp_left",
+            field=models.DecimalField(
+                blank=True,
+                decimal_places=2,
+                help_text="Left extruder current temperature (°C). H2C only.",
+                max_digits=5,
+                null=True,
+            ),
+        ),
+        migrations.AddField(
+            model_name="printermetrics",
+            name="nozzle_type_left",
+            field=models.CharField(
+                blank=True,
+                help_text="Left nozzle type (e.g. HS01-0.4). H2C only.",
+                max_length=50,
+                null=True,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="filament",
+            name="current_tray_id",
+            field=models.IntegerField(
+                blank=True,
+                help_text="Tray slot index within its AMS unit (0-3 for AMS/AMS 2 Pro, 0 for AMS HT)",
+                null=True,
+            ),
+        ),
+    ]