Add printer lifecycle fields and printer log

- Printer: bought_at, last_maintenance_at, decommissioned_at (all Date, nullable)
- PrinterLog: per-printer timestamped text entries (CASCADE delete)
- Migration 0003: adds columns + printer_logs table
- /printers/{id}: detail page showing lifecycle info + scrollable log
- POST /printers/{id}/log: add a log entry via modal form
- Printer names in list are now links to the detail page
- Add Printer modal includes optional purchase date

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/models/printer.py

@@ -1,7 +1,7 @@
 import enum
-from datetime import datetime
+from datetime import date, datetime
 
-from sqlalchemy import DateTime, Enum, ForeignKey, String, func
+from sqlalchemy import Date, DateTime, Enum, ForeignKey, String, func
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.models.base import Base
@@ -24,6 +24,9 @@ class Printer(Base):
     status: Mapped[PrinterStatus] = mapped_column(
         Enum(PrinterStatus), default=PrinterStatus.offline
     )
+    bought_at: Mapped[date | None] = mapped_column(Date)
+    last_maintenance_at: Mapped[date | None] = mapped_column(Date)
+    decommissioned_at: Mapped[date | None] = mapped_column(Date)
     created_at: Mapped[datetime] = mapped_column(DateTime, server_default=func.now())
     updated_at: Mapped[datetime] = mapped_column(
         DateTime, server_default=func.now(), onupdate=func.now()
@@ -32,3 +35,6 @@ class Printer(Base):
     printer_type: Mapped["PrinterType | None"] = relationship(back_populates="printers")
     jobs: Mapped[list["PrintJob"]] = relationship(back_populates="printer")
     todos: Mapped[list["Todo"]] = relationship(back_populates="printer")
+    logs: Mapped[list["PrinterLog"]] = relationship(
+        back_populates="printer", order_by="PrinterLog.created_at.desc()"
+    )