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>

shopdb/plugins/alembic_template.py

@@ -35,7 +35,7 @@ PLUGIN_TABLE_OWNERS: dict[str, Iterable[str]] = {
     'equipment':     ('equipmenttypes', 'equipment'),
     'network':       ('networkdevicetypes', 'networkdevices', 'vlans', 'subnets'),
     'notifications': ('notificationtypes', 'notifications'),
-    'printers':      ('printertypes', 'printers', 'printerdata', 'modelsupplies'),
+    'printers':      ('printertypes', 'printers', 'modelsupplies'),
     'usb':           ('usbdevicetypes', 'usbdevices', 'usbcheckouts'),
 }