feat(article): implement articlesupplier editor tab

- ApiClient: add getSuppliers, addSupplier, updateSupplier,
  orderSuppliers, deleteSupplier on article namespace
- api/index.js: expose same methods in legacy http client
- StorageManager: add #supplierWatchers Map and watchArticleSuppliers()
  backed by article-<sku> SSE signal; wired up as article.supplierWatch
- ArticleTileTab: pass article prop to ArticleSupplierTab
- ArticleSupplierDialog (new): dialog to assign / edit a supplier link
  (supplier autocomplete, Lief.-SKU, VPE, stock, EK Netto + MwSt.)
- ArticleSupplierTab: full supplier management table with reordering
  (up/down arrows → PUT /supplier/order), inline edit and delete,
  stock badge, purchase price display and empty state

src/api/StorageManager.js

@@ -80,11 +80,15 @@ export class StorageManager extends ApiClient {
   #articleWatchers = new Map();
   /** @type {Map<string, Set<() => void>>} sku → history refreshers */
   #historyWatchers = new Map();
+  /** @type {Map<string, Set<() => void>>} sku → supplier refreshers */
+  #supplierWatchers = new Map();
 
   constructor(baseUrl = window.location.origin) {
     super(baseUrl);
     this.#initCaches();
     this.article.watch = (sku, onArticle) => this.watchArticle(sku, onArticle);
+    this.article.supplierWatch = (sku, onSuppliers) =>
+      this.watchArticleSuppliers(sku, onSuppliers);
   }
 
   /** Settled article detail for sku, or undefined. */
@@ -124,7 +128,10 @@ export class StorageManager extends ApiClient {
    */
   watchArticle(sku, onArticle) {
     const key = String(sku);
-    const needListen = !this.#articleWatchers.has(key) && !this.#historyWatchers.has(key);
+    const needListen =
+      !this.#articleWatchers.has(key) &&
+      !this.#historyWatchers.has(key) &&
+      !this.#supplierWatchers.has(key);
 
     let watchers = this.#articleWatchers.get(key);
     if (!watchers) {
@@ -144,7 +151,10 @@ export class StorageManager extends ApiClient {
         set.delete(onArticle);
         if (set.size === 0) {
           this.#articleWatchers.delete(key);
-          if (!this.#historyWatchers.has(key)) {
+          if (
+            !this.#historyWatchers.has(key) &&
+            !this.#supplierWatchers.has(key)
+          ) {
             this.#events?.removeEventListener(`article-${key}`, this.#onArticleSignal);
           }
         }
@@ -214,7 +224,10 @@ export class StorageManager extends ApiClient {
         notifyError(err);
       });
 
-    const needListen = !this.#articleWatchers.has(key) && !this.#historyWatchers.has(key);
+    const needListen =
+      !this.#articleWatchers.has(key) &&
+      !this.#historyWatchers.has(key) &&
+      !this.#supplierWatchers.has(key);
 
     let watchers = this.#historyWatchers.get(key);
     if (!watchers) {
@@ -236,7 +249,10 @@ export class StorageManager extends ApiClient {
         set.delete(run);
         if (set.size === 0) {
           this.#historyWatchers.delete(key);
-          if (!this.#articleWatchers.has(key)) {
+          if (
+            !this.#articleWatchers.has(key) &&
+            !this.#supplierWatchers.has(key)
+          ) {
             this.#events?.removeEventListener(`article-${key}`, this.#onArticleSignal);
           }
         }
@@ -249,6 +265,68 @@ export class StorageManager extends ApiClient {
     };
   }
 
+  /**
+   * Load suppliers for an article and refetch on SSE `article-<sku>`.
+   * @param {string} sku
+   * @param {(suppliers: Array<object>) => void} onSuppliers
+   * @returns {{ unwatch: () => void, refresh: () => Promise<void> }}
+   */
+  watchArticleSuppliers(sku, onSuppliers) {
+    const key = String(sku);
+    let active = true;
+
+    const refresh = async () => {
+      const res = await this.article.getSuppliers(key);
+      if (!active) return;
+      requireObject(res, 'GET /api/article/{sku}/supplier');
+      const list = requireArray(res.suppliers, 'suppliers');
+      onSuppliers(list);
+    };
+
+    const run = () => {
+      void refresh().catch((err) => {
+        if (!active) return;
+        notifyError(err);
+      });
+    };
+
+    const needListen =
+      !this.#articleWatchers.has(key) &&
+      !this.#historyWatchers.has(key) &&
+      !this.#supplierWatchers.has(key);
+
+    let watchers = this.#supplierWatchers.get(key);
+    if (!watchers) {
+      watchers = new Set();
+      this.#supplierWatchers.set(key, watchers);
+    }
+    watchers.add(run);
+    if (needListen) {
+      this.#events?.addEventListener(`article-${key}`, this.#onArticleSignal);
+    }
+
+    run();
+
+    return {
+      refresh,
+      unwatch: () => {
+        active = false;
+        const set = this.#supplierWatchers.get(key);
+        if (!set) return;
+        set.delete(run);
+        if (set.size === 0) {
+          this.#supplierWatchers.delete(key);
+          if (
+            !this.#articleWatchers.has(key) &&
+            !this.#historyWatchers.has(key)
+          ) {
+            this.#events?.removeEventListener(`article-${key}`, this.#onArticleSignal);
+          }
+        }
+      },
+    };
+  }
+
   #onArticleSignal = (event) => {
     const sku = event.type.slice('article-'.length);
     if (this.#articleWatchers.has(sku)) {
@@ -258,6 +336,10 @@ export class StorageManager extends ApiClient {
     if (historyWatchers) {
       for (const run of historyWatchers) run();
     }
+    const supplierWatchers = this.#supplierWatchers.get(sku);
+    if (supplierWatchers) {
+      for (const run of supplierWatchers) run();
+    }
   };
 
   /** Patch local articleIndex name if already loaded; no-op otherwise. */
@@ -393,6 +475,7 @@ export class StorageManager extends ApiClient {
     for (const sku of new Set([
       ...this.#articleWatchers.keys(),
       ...this.#historyWatchers.keys(),
+      ...this.#supplierWatchers.keys(),
     ])) {
       es.addEventListener(`article-${sku}`, this.#onArticleSignal);
     }