Add Columbia catalog mapper, shared upsert, and sync service

Phase 2: the mapping and sync core.

- ColumbiaCatalogMapper (pure/static, unit-tested): maps an API product to a
  PowderCatalogItem. Derives manufacturer (PPG/KP Pigments/Columbia) from
  taxonomy+SKU; flags additives into the Powder Additives category; takes base
  price from the top-level price with variant fallback; captures variation /
  tiered pricing as JSON; parses the free-text cure schedule into all curves
  (three degree glyphs, @/at, multi-curve in order, partial-cure -> none) with
  the first as the primary temp/time; strips HTML descriptions; joins color
  groups; normalizes chemistry; flags clear-coat powders.

- PowderCatalogUpsertService (IPowderCatalogUpsertService): single upsert path
  matching on (VendorName, SKU). Copies only feed-sourced fields and leaves
  enrichment fields (specific gravity, coverage, transfer efficiency, finish)
  untouched so syncs never wipe lazily-enriched TDS/AI data.

- ColumbiaCatalogSyncService (IColumbiaCatalogSyncService): pulls the full
  catalog, maps + de-dupes, upserts, then reconciles discontinuations ONLY on a
  complete pull (a partial pull throws and aborts before the sweep). Reactivates
  reappearing items; records last-synced/last-result platform settings.

- 25 mapper unit tests covering the cure parser, manufacturer derivation,
  simple/variable pricing, chemistry, color, and HTML cases from real records.
  Full suite green (261 passed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Application/Interfaces/IColumbiaCatalogSyncService.cs

@@ -0,0 +1,41 @@
+namespace PowderCoating.Application.Interfaces;
+
+/// <summary>
+/// Orchestrates a full Columbia Coatings catalog sync: pull every product, map and upsert it, then
+/// (only on a complete pull) reconcile discontinuations. Used by both the scheduled background job
+/// and the manual "Sync now" admin action.
+/// </summary>
+public interface IColumbiaCatalogSyncService
+{
+    /// <summary>
+    /// Runs one full sync. Assumes the caller has already decided it should run (enabled / due).
+    /// Returns a result describing the outcome; never throws for an expected failure (not
+    /// configured, partial pull, HTTP error) — those are reported on the result instead.
+    /// </summary>
+    Task<ColumbiaSyncResult> RunSyncAsync(CancellationToken cancellationToken = default);
+}
+
+/// <summary>Outcome of a Columbia catalog sync run.</summary>
+public class ColumbiaSyncResult
+{
+    public bool Success { get; set; }
+    public string? ErrorMessage { get; set; }
+
+    public int TotalFetched { get; set; }
+    public int Inserted { get; set; }
+    public int Updated { get; set; }
+    public int Unchanged { get; set; }
+    public int Skipped { get; set; }
+    public int Discontinued { get; set; }
+    public int Reactivated { get; set; }
+
+    public DateTime StartedAt { get; set; }
+    public TimeSpan Duration { get; set; }
+
+    /// <summary>One-line summary suitable for storing in the last-result platform setting / UI.</summary>
+    public string Summary =>
+        Success
+            ? $"{TotalFetched} fetched: {Inserted} new, {Updated} updated, {Unchanged} unchanged, " +
+              $"{Discontinued} discontinued, {Reactivated} reactivated ({Duration.TotalSeconds:F0}s)"
+            : $"Failed: {ErrorMessage}";
+}

src/PowderCoating.Application/Interfaces/IPowderCatalogUpsertService.cs

@@ -0,0 +1,32 @@
+using PowderCoating.Core.Entities;
+
+namespace PowderCoating.Application.Interfaces;
+
+/// <summary>
+/// Shared upsert for the platform powder catalog: matches incoming records to existing rows by
+/// (VendorName, SKU), inserts new ones, and updates changed ones in place. Used by BOTH the manual
+/// JSON file import and the Columbia API sync so there is a single upsert path, only the mapping
+/// differs. Does NOT handle discontinuation — that is a sync-specific concern.
+/// </summary>
+public interface IPowderCatalogUpsertService
+{
+    /// <summary>
+    /// Applies <paramref name="incoming"/> mapped catalog items. Only fields sourced from the feed
+    /// are copied on update; enrichment fields (specific gravity, coverage, transfer efficiency,
+    /// finish) are preserved so they are not wiped by a feed that never carries them. Changed and
+    /// inserted rows get <paramref name="runTimestamp"/> stamped on LastSyncedAt/UpdatedAt.
+    /// </summary>
+    Task<PowderCatalogUpsertResult> UpsertAsync(
+        IReadOnlyList<PowderCatalogItem> incoming,
+        DateTime runTimestamp,
+        CancellationToken cancellationToken = default);
+}
+
+/// <summary>Counts from an upsert run.</summary>
+public class PowderCatalogUpsertResult
+{
+    public int Inserted { get; set; }
+    public int Updated { get; set; }
+    public int Unchanged { get; set; }
+    public int Skipped { get; set; }
+}