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.Web/Controllers/CompanySettingsController.cs

@@ -35,6 +35,7 @@ public class CompanySettingsController : Controller
     private readonly SignInManager<ApplicationUser> _signInManager;
     private readonly IAzureBlobStorageService _blobStorage;
     private readonly ICustomFormulaAiService _formulaAiService;
+    private readonly IFormulaLibraryService _formulaLibraryService;
 
     public CompanySettingsController(
         IUnitOfWork unitOfWork,
@@ -49,7 +50,8 @@ public class CompanySettingsController : Controller
         UserManager<ApplicationUser> userManager,
         SignInManager<ApplicationUser> signInManager,
         IAzureBlobStorageService blobStorage,
-        ICustomFormulaAiService formulaAiService)
+        ICustomFormulaAiService formulaAiService,
+        IFormulaLibraryService formulaLibraryService)
     {
         _unitOfWork = unitOfWork;
         _mapper = mapper;
@@ -64,6 +66,7 @@ public class CompanySettingsController : Controller
         _signInManager = signInManager;
         _blobStorage = blobStorage;
         _formulaAiService = formulaAiService;
+        _formulaLibraryService = formulaLibraryService;
     }
 
     /// <summary>
@@ -3080,6 +3083,11 @@ public class CompanySettingsController : Controller
 
         _mapper.Map(dto, entity);
         entity.UpdatedAt = DateTime.UtcNow;
+
+        // If this was imported from the library, mark it as modified so the share button appears
+        if (entity.SourceFormulaLibraryItemId.HasValue)
+            entity.IsModifiedFromSource = true;
+
         await _unitOfWork.CompleteAsync();
 
         return Json(new { success = true });
@@ -3100,6 +3108,52 @@ public class CompanySettingsController : Controller
         return Json(new { success = true });
     }
 
+    // ── Community Library: share / unshare / status ───────────────────────
+
+    /// <summary>
+    /// Returns the community library status for a given template: whether it is published,
+    /// eligible to share, and where it was originally imported from if applicable.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> FormulaLibraryStatus(int templateId)
+    {
+        if (!AllowCustomFormulas()) return Json(new { canShare = false });
+        var companyId = _tenantContext.GetCurrentCompanyId()!.Value;
+        var status = await _formulaLibraryService.GetTemplateLibraryStatusAsync(templateId, companyId);
+        return Json(status);
+    }
+
+    /// <summary>
+    /// Publishes a company template to the community library (or re-publishes after unshare).
+    /// Only templates that are original creations or modified imports may be shared.
+    /// </summary>
+    [HttpPost]
+    public async Task<IActionResult> ShareFormula([FromBody] PowderCoating.Application.DTOs.Company.ShareFormulaRequest request)
+    {
+        if (!AllowCustomFormulas()) return Json(new { success = false, message = "Custom Formulas are not available on your current plan." });
+        var companyId = _tenantContext.GetCurrentCompanyId()!.Value;
+        var userId = User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value ?? "";
+
+        try
+        {
+            var libraryItemId = await _formulaLibraryService.ShareAsync(companyId, userId, request);
+            return Json(new { success = true, libraryItemId });
+        }
+        catch (InvalidOperationException ex)
+        {
+            return Json(new { success = false, message = ex.Message });
+        }
+    }
+
+    /// <summary>Removes a template from the community library. Existing company imports are unaffected.</summary>
+    [HttpPost]
+    public async Task<IActionResult> UnshareFormula(int libraryItemId)
+    {
+        var companyId = _tenantContext.GetCurrentCompanyId()!.Value;
+        await _formulaLibraryService.UnshareAsync(libraryItemId, companyId);
+        return Json(new { success = true });
+    }
+
     /// <summary>
     /// Uploads a diagram image for a template to blob storage container
     /// <c>formulatemplate-diagrams/{companyId}/{templateId}/diagram.{ext}</c>.