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.Application/DTOs/Company/FormulaLibraryDtos.cs

@@ -0,0 +1,69 @@
+namespace PowderCoating.Application.DTOs.Company;
+
+// ── Browse / card display ──────────────────────────────────────────────────
+
+/// <summary>Lean DTO for the community library browse grid card.</summary>
+public class FormulaLibraryCardDto
+{
+    public int Id { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public string? Description { get; set; }
+    public string OutputMode { get; set; } = "FixedRate";
+    public string? Tags { get; set; }
+    public string? IndustryHint { get; set; }
+    public string SourceCompanyName { get; set; } = string.Empty;
+    public int ImportCount { get; set; }
+    public DateTime SharedAt { get; set; }
+    public string? DiagramImagePath { get; set; }
+
+    /// <summary>Non-null when this formula was derived from another library entry.</summary>
+    public int? InspiredByFormulaLibraryItemId { get; set; }
+    public string? InspiredByName { get; set; }
+    public string? InspiredByCompanyName { get; set; }
+
+    /// <summary>True when the current company has already imported this entry.</summary>
+    public bool AlreadyImported { get; set; }
+
+    /// <summary>True when this formula was shared by the current browsing company.</summary>
+    public bool IsOwnFormula { get; set; }
+}
+
+// ── Full detail (import preview modal) ────────────────────────────────────
+
+/// <summary>Full DTO used in the import preview modal — shows fields and formula.</summary>
+public class FormulaLibraryDetailDto : FormulaLibraryCardDto
+{
+    public string FieldsJson { get; set; } = "[]";
+    public string Formula { get; set; } = string.Empty;
+    public decimal? DefaultRate { get; set; }
+    public string? RateLabel { get; set; }
+    public string? Notes { get; set; }
+    public int FieldCount { get; set; }
+}
+
+// ── Share from Company Settings ───────────────────────────────────────────
+
+/// <summary>Submitted when a company admin shares one of their templates to the community library.</summary>
+public class ShareFormulaRequest
+{
+    public int CustomItemTemplateId { get; set; }
+    public string? Tags { get; set; }
+    public string? IndustryHint { get; set; }
+}
+
+// ── Company Settings list view ─────────────────────────────────────────────
+
+/// <summary>Status of a template relative to the community library, shown in Company Settings.</summary>
+public class FormulaLibraryStatusDto
+{
+    /// <summary>The FormulaLibraryItem Id, if this template has ever been shared.</summary>
+    public int? LibraryItemId { get; set; }
+    public bool IsPublished { get; set; }
+
+    /// <summary>Whether this template is eligible to be shared (original or modified import).</summary>
+    public bool CanShare { get; set; }
+
+    /// <summary>Set when this template was imported; the name of the original library entry.</summary>
+    public string? ImportedFromName { get; set; }
+    public string? ImportedFromCompany { get; set; }
+}