feat: persistent multi-step undo system in TopBar

fix: save all changes to Supabase with reliable upsert

- Replace broken PATCH→POST fallback with single atomic upsert (POST +
  Prefer: resolution=merge-duplicates). The old PATCH returned 200 OK
  with empty body for new articles, causing silent data loss on every
  first save per article.
- Fix getAllSyncedRows pagination: add explicit limit=10000 and Range
  header to bypass Supabase's default 1000-row cap.
- Add fetchWithRetry helper (2 retries on 5xx/network errors).
- handleSaveRow now returns Promise<boolean> and closes EditPanel only
  after a confirmed successful save.
- Add 'error' save status: failed rows turn red (border-l-red-500)
  across ProductDescriptions, ArticleDetails, and PricingView.
- EditPanel shows saving spinner, disables buttons while saving, and
  displays inline error message with "Retry Save" on failure.

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

src/lib/supabase.ts

@@ -3,14 +3,40 @@ import { ExcelRow } from '../types';
 const SUPABASE_URL = 'https://hwithddwaapyhnfwcesj.supabase.co';
 const SUPABASE_KEY = 'sb_publishable_fGXkh0bSrAOqSk2jWKAzSg_NJD9YPCv';
 
-export async function saveRowToSupabase(articleNo: string, rowData: ExcelRow) {
+async function fetchWithRetry(
+  url: string,
+  options: RequestInit,
+  retries = 2,
+  delayMs = 1000
+): Promise<Response> {
+  let lastError: Error | null = null;
+  for (let attempt = 0; attempt <= retries; attempt++) {
+    try {
+      const res = await fetch(url, options);
+      if (res.ok || res.status < 500 || attempt === retries) return res;
+    } catch (err) {
+      lastError = err as Error;
+      if (attempt === retries) throw lastError;
+    }
+    await new Promise(r => setTimeout(r, delayMs));
+  }
+  throw lastError ?? new Error('fetch failed');
+}
+
+export async function saveRowToSupabase(articleNo: string, rowData: ExcelRow): Promise<boolean> {
   try {
-    const response = await fetch(`${SUPABASE_URL}/rest/v1/products_sync?id=eq.${encodeURIComponent(articleNo)}`, {
-      method: 'PATCH',
+    // Single upsert: POST with Prefer=resolution=merge-duplicates
+    // This handles both INSERT (new article) and UPDATE (existing) atomically.
+    // The old PATCH approach silently failed for new articles because Supabase
+    // returns 200 OK with an empty body when no rows match — indistinguishable
+    // from a successful update.
+    const response = await fetchWithRetry(`${SUPABASE_URL}/rest/v1/products_sync`, {
+      method: 'POST',
       headers: {
         'apikey': SUPABASE_KEY,
         'Authorization': `Bearer ${SUPABASE_KEY}`,
-        'Content-Type': 'application/json'
+        'Content-Type': 'application/json',
+        'Prefer': 'resolution=merge-duplicates'
       },
       body: JSON.stringify({
         id: articleNo,
@@ -21,32 +47,9 @@ export async function saveRowToSupabase(articleNo: string, rowData: ExcelRow) {
     });
 
     if (!response.ok) {
-        const errorData = await response.json().catch(() => ({}));
-        console.error('Initial PATCH failed:', response.status, errorData);
-
-        // If PATCH didn't find the record, try UPSERT
-        const upsertResponse = await fetch(`${SUPABASE_URL}/rest/v1/products_sync`, {
-          method: 'POST',
-          headers: {
-            'apikey': SUPABASE_KEY,
-            'Authorization': `Bearer ${SUPABASE_KEY}`,
-            'Content-Type': 'application/json',
-            'Prefer': 'resolution=merge-duplicates'
-          },
-          body: JSON.stringify({
-            id: articleNo,
-            data: rowData,
-            status_check: 'pending',
-            updated_at: new Date().toISOString()
-          })
-        });
-
-        if (!upsertResponse.ok) {
-          const upsertError = await upsertResponse.json().catch(() => ({}));
-          console.error('UPSERT failed:', upsertResponse.status, upsertError);
-          return false;
-        }
-        return true;
+      const errorData = await response.json().catch(() => ({}));
+      console.error('Supabase upsert failed:', response.status, errorData);
+      return false;
     }
     return true;
   } catch (error) {
@@ -57,21 +60,26 @@ export async function saveRowToSupabase(articleNo: string, rowData: ExcelRow) {
 
 export async function getAllSyncedRows(): Promise<Record<string, { data: ExcelRow, status: string }>> {
   try {
-    const response = await fetch(`${SUPABASE_URL}/rest/v1/products_sync`, {
-      headers: {
-        'apikey': SUPABASE_KEY,
-        'Authorization': `Bearer ${SUPABASE_KEY}`
+    // Explicit limit to avoid Supabase's default 1000-row cap
+    const response = await fetch(
+      `${SUPABASE_URL}/rest/v1/products_sync?select=id,data,status_check&limit=10000`,
+      {
+        headers: {
+          'apikey': SUPABASE_KEY,
+          'Authorization': `Bearer ${SUPABASE_KEY}`,
+          'Range': '0-9999'
+        }
       }
-    });
+    );
 
     if (!response.ok) return {};
 
     const data = await response.json();
     const result: Record<string, { data: ExcelRow, status: string }> = {};
     data.forEach((item: any) => {
-      result[item.id] = { 
-        data: item.data, 
-        status: item.status_check || 'original' 
+      result[item.id] = {
+        data: item.data,
+        status: item.status_check || 'original'
       };
     });
     return result;
@@ -81,7 +89,7 @@ export async function getAllSyncedRows(): Promise<Record<string, { data: ExcelRo
   }
 }
 
-export async function resetAllPendingRows() {
+export async function resetAllPendingRows(): Promise<boolean> {
   try {
     const response = await fetch(`${SUPABASE_URL}/rest/v1/products_sync?status_check=eq.pending`, {
       method: 'PATCH',