feat(adapters): mark EBA-superseded adapters as legacy and collapse them

The 12 old adapters that now have an EBA replacement are tagged
`spec.legacy: true` in their source manifests. Principle: don't delete,
de-emphasize.

- sources/*.yaml (aiocqhttp, dingtalk, discord, kook, lark,
  officialaccount, qqofficial, slack, telegram, wecom, wecombot,
  wecomcs): add spec.legacy: true
- Adapter / IChooseAdapterEntity types: add optional legacy flag
- BotForm adapter Select: split legacy adapters into a collapsed,
  grayscale group at the bottom with an explanatory hint; auto-expand
  when the bot already uses a legacy adapter
- Wizard platform picker: same collapsed legacy section
- i18n: legacyAdapters / legacyAdaptersHint (zh-Hans, en-US)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/app/infra/entities/api/index.ts

@@ -205,6 +205,7 @@ export interface Adapter {
   icon?: string;
   spec: {
     categories?: string[];
+    legacy?: boolean;
     help_links?: Record<string, string>;
     supported_events?: string[];
     supported_apis?: string[];