feat: add API config system, FilePipe backend, and ConfigManager

- ConfigManager: route sensitive keys (API keys) to localStorage,
  migrate existing values out of extension_settings on startup
- ApiKeyStore: local/cloud storage modes with RSA+AES hybrid encryption
- ApiProfileManager: named connection profiles (chat/embedding/rerank)
  with per-slot type-validated assignments
- FilePipe: complete IndexedDB backend (read/write/delete/list/stat)
- Amily2Bus: inject FilePipe via forPlugin() capability token
- UI: api-config-panel with profile CRUD and slot assignment
- TableSystemService: initial service layer scaffold
- logger.js: XSS fix

assets/amily2-modal.html

@@ -235,6 +235,13 @@
     </div>
 </fieldset>
 
+<fieldset class="settings-group">
+    <legend><i class="fas fa-shield-alt"></i> 系统配置</legend>
+    <div class="button-group" style="display: flex; justify-content: space-between; gap: 8px;">
+        <button id="amily2_open_api_config" class="menu_button wide_button"><i class="fas fa-key"></i> API 连接配置</button>
+    </div>
+</fieldset>
+
 <hr class="header-divider">