feat(domain,application,infrastructure,backend,web-server,app-tauri,frontend): bibliothèque d'icônes projet personnalisées importées par l'utilisateur — #358 (QA verte)

domain: variante ProjectIconSet::Custom, métadonnées CustomProjectIconAsset (id opaque, media type png/jpeg/webp, byte_size, dimensions décodées, sha256, nom de fichier original sans chemin, created_at), CustomProjectIconContent et port CustomProjectIconAssetStore (list/read/exists/create/delete) avec CustomProjectIconStoreError dédiée.
application: use case project_icon_assets — import validé png/jpeg/webp avec rejet du contenu SVG, dimensionnement et digest sha256, bibliothèque partagée à l'instance indépendante de tout projet, suppression refusée tant que l'asset est référencé par un projet.
infrastructure: store fichier store/project_icon_asset.rs — index canonique + octets, création atomique sous extension validée.
backend/web-server: contrat HTTP /api/project-icon-assets (GET liste, POST import, GET lecture, GET /usage, DELETE) avec prévol OPTIONS et tests contrat incluant le rejet SVG.
app-tauri: commandes import/list/read/get_usage/delete_custom_project_icon_asset exposées au frontend.
frontend: port ProjectIconAssetGateway (list/import/delete/getUrl sans exposer de chemin filesystem), gateways http+mock avec tests, DI, section Icônes personnalisées du ProjectIconPicker (import fichier accept png/jpeg/webp, sélection role=option, suppression avec retrait de sélection, erreurs lisibles i18n FR/EN), tests projectIcons étendus.

QA verte: contrats HTTP et Tauri identiques, suites cargo et npm ciblées vertes.

frontend/src/adapters/mock/index.ts

@@ -138,6 +138,8 @@ import type {
   OpenTerminalOptions,
   ProfileGateway,
   ProjectGateway,
+  ProjectIconAssetGateway,
+  CustomProjectIconAsset,
   ProjectSettings,
   PermissionGateway,
   PluginConfigDocumentReadInput,
@@ -1287,6 +1289,59 @@ export class MockTerminalGateway implements TerminalGateway {
   }
 }
 
+export class MockProjectIconAssetGateway implements ProjectIconAssetGateway {
+  private readonly assets = new Map<string, CustomProjectIconAsset>();
+  private readonly urls = new Map<string, string>();
+  private sequence = 0;
+
+  async list(): Promise<CustomProjectIconAsset[]> {
+    return [...this.assets.values()].map((asset) => ({ ...asset }));
+  }
+
+  async import(file: File): Promise<CustomProjectIconAsset> {
+    if (!["image/png", "image/jpeg", "image/webp"].includes(file.type)) {
+      throw { code: "INVALID_ICON_MEDIA_TYPE", message: "PNG, JPEG or WebP required" } as GatewayError;
+    }
+    if (file.size > 2 * 1024 * 1024) {
+      throw { code: "ICON_TOO_LARGE", message: "Icon exceeds 2 MiB" } as GatewayError;
+    }
+    const id = `mock-icon-${++this.sequence}`;
+    const asset: CustomProjectIconAsset = {
+      id,
+      mediaType: file.type as CustomProjectIconAsset["mediaType"],
+      byteSize: file.size,
+      width: 0,
+      height: 0,
+      sha256: `mock-${id}`,
+      originalFilename: file.name,
+      createdAt: Date.now(),
+      usedByProjectCount: 0,
+    };
+    this.assets.set(id, asset);
+    const createObjectURL = URL.createObjectURL?.bind(URL);
+    this.urls.set(id, createObjectURL ? createObjectURL(file) : `data:${file.type};base64,`);
+    return { ...asset };
+  }
+
+  async delete(assetId: string): Promise<void> {
+    const asset = this.assets.get(assetId);
+    if (!asset) throw { code: "NOT_FOUND", message: `icon ${assetId} not found` } as GatewayError;
+    if (asset.usedByProjectCount > 0) {
+      throw { code: "CUSTOM_ICON_IN_USE", message: `icon is used by ${asset.usedByProjectCount} projects` } as GatewayError;
+    }
+    const url = this.urls.get(assetId);
+    if (url?.startsWith("blob:")) URL.revokeObjectURL?.(url);
+    this.assets.delete(assetId);
+    this.urls.delete(assetId);
+  }
+
+  async getUrl(assetId: string): Promise<string> {
+    const url = this.urls.get(assetId);
+    if (!url) throw { code: "NOT_FOUND", message: `icon ${assetId} not found` } as GatewayError;
+    return url;
+  }
+}
+
 export class MockProjectGateway implements ProjectGateway {
   private projects: Project[] = [];
   private contexts = new Map<string, string>();
@@ -5002,6 +5057,7 @@ export function createMockGateways(): Gateways {
     input: new MockInputGateway(),
     terminal: new MockTerminalGateway(),
     project: new MockProjectGateway(),
+    projectIconAsset: new MockProjectIconAssetGateway(),
     layout: new MockLayoutGateway(),
     git: new MockGitGateway(),
     remote: new MockRemoteGateway(),