Add Employee Timeclock feature with kiosk, attendance report, and payroll CSV export

- New EmployeeClockEntry entity (facility-level attendance, separate from job time entries)
- KioskPin added to ApplicationUser; TimeclockKioskToken added to Company
- TimeclockController: clock in/out, who's in, 14-day history, manager edit/delete,
  tablet kiosk with device-cookie auth, PIN management via Users edit page
- Kiosk UI: employee tile grid + 4-digit PIN pad + auto-detect clock-in vs clock-out
- Attendance report at /Reports/Attendance with weekly subtotal rows
- Payroll CSV export at /Reports/AttendanceCsv (flat, one row per segment)
- AllowCustomFormulas wired through PlatformSubscriptionController + subscription views
- Fix soft-delete bug on CustomItemTemplate (missing HasQueryFilter in OnModelCreating)
- Help article (Help/Timeclock.cshtml) and AI knowledge base updated
- Migrations: AddEmployeeTimeclock, AddTimeclockKioskToken

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

src/PowderCoating.Infrastructure/Services/CustomFormulaAiService.cs

@@ -51,11 +51,17 @@ Respond ONLY with a valid JSON object matching this exact schema — no markdown
   ""verificationResult"": number
 }
 
+Built-in shop-rate variables (injected automatically at eval time — do NOT redeclare them as fields):
+  standard_labor_rate       — shop billing rate in $/hr (e.g.  hours * standard_labor_rate)
+  additional_coat_labor_pct — extra-coat labor surcharge 0–100 (e.g.  cost * (1 + additional_coat_labor_pct/100))
+  markup_pct                — general markup percentage 0–100   (e.g.  cost * (1 + markup_pct/100))
+
 Rules:
 - Use FixedRate when the formula directly calculates a dollar amount (e.g. surface area × rate per sqft)
 - Use SurfaceAreaSqFt when the formula calculates square footage and the standard pricing engine handles the rest
-- Always include a 'rate' variable when outputMode is FixedRate and the price scales with dimensions
+- Always include a 'rate' variable when outputMode is FixedRate and the price scales with dimensions, UNLESS the formula already uses standard_labor_rate or another built-in
 - Field names must be valid NCalc identifiers (letters, digits, underscores; no spaces or hyphens)
+- Do NOT include standard_labor_rate, additional_coat_labor_pct, or markup_pct in the fields array — they are injected automatically
 - verificationInputs and verificationResult must use the exact field names and formula you generated
 - Surface area formulas for box shapes: 2*(L*W + L*H + W*H) where L/W/H are in the same unit; convert to sqft if needed
 - For inch inputs convert to sqft: divide by 144 (sqin→sqft) or use /12 per side before multiplying