fix: 支持 wxgf 原图解密并修复缩略图缓存刷新

- 增加 wxgf/HEVC 图片转换支持
- 增加 FFmpeg 跨平台安装、目录填写与能力检测
- 避免缩略图占用原图缓存，下载原图后可即时刷新
- 移除聊天图片的缩略图角标

(cherry picked from commit 4cee159a65496bd30dd690b568c47a120f3fff30)

src/preload/index.d.ts

@@ -14,6 +14,8 @@ import type {
   DatabaseKeyValidationResult
 } from '../shared/database-key'
 import type {
+  ImageDecoderSelectionResult,
+  ImageDecoderStatus,
   ImageDecryptionStatus,
   ImageDecryptionTestResult,
   ImageKeyConfigResult,
@@ -260,6 +262,7 @@ declare global {
           apiHost: string
           apiPort: number
           imageKeyRoot: string
+          ffmpegPath: string
           recallProtectionEnabled: boolean
           debugEnabled: boolean
           autoLogin: boolean
@@ -273,6 +276,9 @@ declare global {
       }>
       getImageKeyConfig: () => Promise<ImageKeyConfigResult>
       getImageDecryptionStatus: () => Promise<ImageDecryptionStatus>
+      selectImageDecoder: () => Promise<ImageDecoderSelectionResult>
+      getImageDecoderStatus: () => Promise<ImageDecoderStatus>
+      openImageDecoderDownload: () => Promise<{ success: boolean; error?: string }>
       saveImageKeyConfig: (request: SaveImageKeyRequest) => Promise<ImageKeyConfigResult>
       testImageDecryption: (
         request: TestImageDecryptionRequest
@@ -291,6 +297,7 @@ declare global {
           apiHost: string
           apiPort: number
           imageKeyRoot: string
+          ffmpegPath: string
           recallProtectionEnabled: boolean
           debugEnabled: boolean
           autoLogin: boolean
@@ -310,6 +317,7 @@ declare global {
           apiHost: string
           apiPort: number
           imageKeyRoot: string
+          ffmpegPath: string
           recallProtectionEnabled: boolean
           debugEnabled: boolean
           autoLogin: boolean
@@ -327,6 +335,7 @@ declare global {
           apiHost: string
           apiPort: number
           imageKeyRoot: string
+          ffmpegPath: string
           recallProtectionEnabled: boolean
           debugEnabled: boolean
           autoLogin: boolean