Fix printer deletion freeze and allow multiple smart plugs per printer (Issue #214)

Bug 1: Delete printer was not actually deleting archives when
delete_archives=True (default). The if-condition was inverted, causing
archives to remain and potentially causing FK constraint issues.

Bug 2: SmartPlug.printer_id had unique=True constraint, preventing
multiple HA scripts from being linked to the same printer. Removed the
constraint to allow multiple plugs/scripts per printer (matching
feature/176 behavior).

Closes #214

backend/app/api/routes/printers.py

@@ -175,7 +175,10 @@ async def delete_printer(
 
     printer_manager.disconnect_printer(printer_id)
 
-    if not delete_archives:
+    if delete_archives:
+        # Delete all archives for this printer
+        await db.execute(sql_delete(PrintArchive).where(PrintArchive.printer_id == printer_id))
+    else:
         # Orphan the archives instead of deleting them
         from sqlalchemy import update
 

backend/app/models/printer.py

@@ -40,7 +40,7 @@ class Printer(Base):
 
     # Relationships
     archives: Mapped[list["PrintArchive"]] = relationship(back_populates="printer", cascade="all, delete-orphan")
-    smart_plug: Mapped["SmartPlug | None"] = relationship(back_populates="printer", uselist=False)
+    smart_plugs: Mapped[list["SmartPlug"]] = relationship(back_populates="printer")
     notification_providers: Mapped[list["NotificationProvider"]] = relationship(back_populates="printer")
     maintenance_items: Mapped[list["PrinterMaintenance"]] = relationship(
         back_populates="printer", cascade="all, delete-orphan"

backend/app/models/smart_plug.py

@@ -50,10 +50,8 @@ class SmartPlug(Base):
     # Legacy multiplier - kept for backward compatibility
     mqtt_multiplier: Mapped[float] = mapped_column(Float, default=1.0)  # Deprecated, use mqtt_power_multiplier
 
-    # Link to printer (1:1)
-    printer_id: Mapped[int | None] = mapped_column(
-        ForeignKey("printers.id", ondelete="SET NULL"), unique=True, nullable=True
-    )
+    # Link to printer (multiple plugs/scripts can be linked to one printer)
+    printer_id: Mapped[int | None] = mapped_column(ForeignKey("printers.id", ondelete="SET NULL"), nullable=True)
 
     # Automation settings
     enabled: Mapped[bool] = mapped_column(Boolean, default=True)
@@ -100,7 +98,7 @@ class SmartPlug(Base):
     updated_at: Mapped[datetime] = mapped_column(DateTime, server_default=func.now(), onupdate=func.now())
 
     # Relationship
-    printer: Mapped["Printer"] = relationship(back_populates="smart_plug")
+    printer: Mapped["Printer"] = relationship(back_populates="smart_plugs")
 
 
 from backend.app.models.printer import Printer  # noqa: E402

test_backend.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
 
 cd backend
-../venv/bin/python3 -m pytest tests/ -v
+../venv/bin/python3 -m pytest tests/ -v -n 14
 cd ..