add not-found handling to ZK and hotlink viewer pages.

Rename ViewerView and view store to ZkViewerView and useZkViewStore; unify hotlink load and ZK unlock error copy.

frontend/src/stores/zkView.ts

@@ -0,0 +1,79 @@
+import { defineStore } from 'pinia';
+import { ref } from 'vue';
+import { api } from '@/plugins/axios';
+import type { GetZkUploadCiphertextResult } from '@/types/upload/GetZkUploadCiphertextResult';
+import { base64ToBytes } from '@/utils/encoding/base64ToBytes';
+import { toArrayBuffer } from '@/utils/toArrayBuffer';
+import { decryptPasswordProtectedZkUpload } from '@/utils/upload/decryptPasswordProtectedZkUpload';
+import { decryptZkUpload } from '@/utils/upload/decryptZkUpload';
+
+export const useZkViewStore = defineStore('zkView', () => {
+    const imageObjectUrl = ref<string | null>(null);
+
+    const clearImage = (): void => {
+        if (imageObjectUrl.value) {
+            URL.revokeObjectURL(imageObjectUrl.value);
+            imageObjectUrl.value = null;
+        }
+    };
+
+    const fetchZkCiphertext = async (uploadId: string): Promise<GetZkUploadCiphertextResult> => {
+        const { data } = await api.get<GetZkUploadCiphertextResult>(`/uploads/${uploadId}`);
+
+        return data;
+    };
+
+    const loadZk = async (
+        payload: GetZkUploadCiphertextResult,
+        fragmentKey: string,
+        password?: string
+    ): Promise<void> => {
+        clearImage();
+
+        const iv = base64ToBytes(payload.iv);
+        const ciphertext = base64ToBytes(payload.ciphertext);
+
+        let plaintext: Uint8Array;
+
+        if (payload.passwordProtected) {
+            if (!password) {
+                throw new Error('Password required');
+            }
+
+            if (!payload.wrappedDek || !payload.wrapIv || !payload.salt) {
+                throw new Error('Incomplete password protection data');
+            }
+
+            const wrappedDek = base64ToBytes(payload.wrappedDek);
+            const wrapIv = base64ToBytes(payload.wrapIv);
+            const salt = base64ToBytes(payload.salt);
+
+            plaintext = await decryptPasswordProtectedZkUpload(
+                ciphertext,
+                iv,
+                fragmentKey,
+                password,
+                wrappedDek,
+                wrapIv,
+                salt
+            );
+        } else {
+            plaintext = await decryptZkUpload(ciphertext, iv, fragmentKey);
+        }
+
+        const buffer = toArrayBuffer(plaintext);
+
+        if (!buffer) {
+            throw new Error('Could not build image blob');
+        }
+
+        imageObjectUrl.value = URL.createObjectURL(new Blob([buffer]));
+    };
+
+    return {
+        imageObjectUrl,
+        fetchZkCiphertext,
+        loadZk,
+        clearImage
+    };
+});