Add Community Formula Library feature

Companies can now share their custom formula templates to a platform-wide
community library. Other tenants can browse, preview, and import formulas
as independent local copies. Includes attribution (source company name),
"Inspired by" lineage for re-contributed formulas, import counts, own-formula
badge, cascade diagram nullification, and AI assistant + help docs updates.

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

src/PowderCoating.Core/Interfaces/IUnitOfWork.cs

@@ -158,6 +158,10 @@ IRepository<ReworkRecord> ReworkRecords { get; }
     // Custom Formula Templates
     IRepository<CustomItemTemplate> CustomItemTemplates { get; }
 
+    // Formula Community Library
+    IPlainRepository<FormulaLibraryItem> FormulaLibrary { get; }
+    IRepository<FormulaLibraryImport> FormulaLibraryImports { get; }
+
     // Employee Timeclock
     IRepository<EmployeeClockEntry> EmployeeClockEntries { get; }
     IRepository<TimeclockKioskDevice> TimeclockKioskDevices { get; }