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/routers/ui.py

@@ -8,6 +8,7 @@ from app.db import get_db
 from app.models.filament import Filament
 from app.models.print_job import JobStatus, PrintJob
 from app.models.printer import Printer, PrinterStatus
+from app.models.printer_log import PrinterLog
 from app.models.printer_type import PrinterType
 from app.models.pricing import PricingConfig
 from app.models.todo import Todo
@@ -48,18 +49,42 @@ def create_printer(
     name: str = Form(...),
     location: str = Form(""),
     type_id: str = Form(""),
+    bought_at: str = Form(""),
     db: Session = Depends(get_db),
 ):
+    from datetime import date
     printer = Printer(
         name=name.strip(),
         location=location.strip() or None,
         type_id=int(type_id) if type_id else None,
+        bought_at=date.fromisoformat(bought_at) if bought_at else None,
     )
     db.add(printer)
     db.commit()
     return RedirectResponse(url="/printers", status_code=HTTP_303_SEE_OTHER)
 
 
+@router.get("/printers/{printer_id}", response_class=HTMLResponse)
+def printer_detail(printer_id: int, request: Request, db: Session = Depends(get_db)):
+    printer = db.query(Printer).filter(Printer.id == printer_id).first()
+    if not printer:
+        from fastapi import HTTPException
+        raise HTTPException(status_code=404, detail="Printer not found")
+    return templates.TemplateResponse("printer_detail.html", {
+        "request": request,
+        "active": "printers",
+        "printer": printer,
+    })
+
+
+@router.post("/printers/{printer_id}/log")
+def add_printer_log(printer_id: int, message: str = Form(...), db: Session = Depends(get_db)):
+    entry = PrinterLog(printer_id=printer_id, message=message.strip())
+    db.add(entry)
+    db.commit()
+    return RedirectResponse(url=f"/printers/{printer_id}", status_code=HTTP_303_SEE_OTHER)
+
+
 @router.get("/printer-types", response_class=HTMLResponse)
 def printer_types_page(request: Request, db: Session = Depends(get_db)):
     return templates.TemplateResponse("printer_types.html", {