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/core/models/communication.py

@@ -36,14 +36,6 @@ class Communication(BaseModel):
         comment='FK to assets table (new architecture)'
     )
 
-    # Legacy machine FK (for backward compatibility during migration)
-    machineid = db.Column(
-        db.Integer,
-        db.ForeignKey('machines.machineid'),
-        nullable=True,
-        comment='DEPRECATED: FK to machines table - use assetid instead'
-    )
-
     comtypeid = db.Column(
         db.Integer,
         db.ForeignKey('communicationtypes.comtypeid'),
@@ -95,9 +87,8 @@ class Communication(BaseModel):
 
     __table_args__ = (
         db.Index('idx_comm_asset', 'assetid'),
-        db.Index('idx_comm_machine', 'machineid'),
         db.Index('idx_comm_ip', 'ipaddress'),
     )
 
     def __repr__(self):
-        return f"<Communication {self.machineid}:{self.comtype.comtype if self.comtype else 'Unknown'}>"
+        return f"<Communication {self.assetid}:{self.comtype.comtype if self.comtype else 'Unknown'}>"