Retire the legacy Machine model (ADR-001 cutover)

The asset/computer model is now the single source of truth. Remove the Machine
instance layer end to end:

- Delete models Machine, MachineStatus, PCType, MachineRelationship,
  InstalledApp, PrinterData; keep MachineType (models.machinetypeid still
  references it).
- Delete the /api/machines, /api/statuses, /api/pctypes blueprints and the
  legacy /api/printers/legacy (PrinterData) blueprint.
- Drop the deprecated communications.machineid column and its FK.
- Migration 7c01 drops tables machines, machinestatuses, pctypes,
  machinerelationships, installedapps, printerdata (idempotent).
- Fix remaining readers (applications install counts) to ComputerInstalledApp.
- Frontend: remove dead machinesApi/statusesApi/pctypesApi wrappers; repoint
  the PC Types settings page at computer types.

143 tests pass; all asset/computer/dashboard/report/collector endpoints 200.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plugins/printers/plugin.py

@@ -13,8 +13,8 @@ from shopdb.extensions import db
 from shopdb.core.models.machine import MachineType
 from shopdb.core.models import AssetType
 
-from .models import PrinterData, Printer, PrinterType, ModelSupply
-from .api import printers_bp, printers_asset_bp
+from .models import Printer, PrinterType, ModelSupply
+from .api import printers_asset_bp
 from .services import ZabbixService
 
 logger = logging.getLogger(__name__)
@@ -74,9 +74,8 @@ class PrintersPlugin(BasePlugin):
     def get_models(self) -> List[Type]:
         """Return list of SQLAlchemy model classes."""
         return [
-            PrinterData,   # Legacy Machine-based
-            Printer,       # New Asset-based
-            PrinterType,   # New printer type classification
+            Printer,       # Asset-based
+            PrinterType,   # printer type classification
             ModelSupply,   # model -> toner/drum/waste part numbers
         ]
 
@@ -98,9 +97,6 @@ class PrintersPlugin(BasePlugin):
         app.config.setdefault('ZABBIX_URL', '')
         app.config.setdefault('ZABBIX_TOKEN', '')
 
-        # Register legacy blueprint for backward compatibility
-        app.register_blueprint(printers_bp, url_prefix='/api/printers/legacy')
-
         logger.info(f"Printers plugin initialized (v{self.meta.version})")
 
     def on_install(self, app: Flask) -> None: