feat(CUB-28): [Extrudex] Define filament inventory database entities

Add storage_location and is_archived fields to Spool entity to complete
the filament inventory entity definition per CUB-28 requirements.

Changes:
- Spool entity: add IsArchived (bool, default false) and StorageLocation
  (nullable string, max 200) for physical inventory tracking
- SpoolConfiguration: add snake_case column mappings, defaults, and indexes
  (ix_spools_is_archived, ix_spools_active_archived composite)
- FilamentDtos: add IsArchived + StorageLocation to Response, Create, Update
- FilamentQueryDtos: add IncludeArchived and StorageLocation query filters
- FilamentsController: wire new fields into query, create, update, mapping
- FilamentValidators: add StorageLocation max-length validation

Build: PASS (0 errors)

backend/API/DTOs/Filaments/FilamentDtos.cs

@@ -59,6 +59,12 @@ public class FilamentResponse
     /// <summary>Whether the spool is currently active and available.</summary>
     public bool IsActive { get; set; }
 
+    /// <summary>Whether the spool has been archived (removed from active inventory).</summary>
+    public bool IsArchived { get; set; }
+
+    /// <summary>Physical storage location (e.g., "Shelf A", "Drawer 3"). Null if unset.</summary>
+    public string? StorageLocation { get; set; }
+
     /// <summary>Timestamp when this record was created (UTC).</summary>
     public DateTime CreatedAt { get; set; }
 
@@ -133,6 +139,15 @@ public class CreateFilamentRequest
 
     /// <summary>Whether the spool is active. Defaults to true.</summary>
     public bool IsActive { get; set; } = true;
+
+    /// <summary>Whether the spool is archived. Defaults to false.
+    /// </summary>
+    public bool IsArchived { get; set; } = false;
+
+    /// <summary>Physical storage location (e.g., "Shelf A", "Drawer 3"). Optional.
+    /// </summary>
+    [StringLength(200, ErrorMessage = "StorageLocation must not exceed 200 characters.")]
+    public string? StorageLocation { get; set; }
 }
 
 /// <summary>
@@ -196,4 +211,11 @@ public class UpdateFilamentRequest
 
     /// <summary>Whether the spool is active.</summary>
     public bool IsActive { get; set; } = true;
+
+    /// <summary>Whether the spool is archived. Defaults to false.</summary>
+    public bool IsArchived { get; set; } = false;
+
+    /// <summary>Physical storage location (e.g., "Shelf A", "Drawer 3"). Optional.</summary>
+    [StringLength(200, ErrorMessage = "StorageLocation must not exceed 200 characters.")]
+    public string? StorageLocation { get; set; }
 }