feat(telegram): add sticker support with vision caching

Add support for receiving and sending Telegram stickers:

Inbound:
- Receive static WEBP stickers (skip animated/video)
- Process stickers through dedicated vision call for descriptions
- Cache vision descriptions to avoid repeated API calls
- Graceful error handling for fetch failures

Outbound:
- Add sticker action to send stickers by fileId
- Add sticker-search action to find cached stickers by query
- Accept stickerId from shared schema, convert to fileId

Cache:
- Store sticker metadata (fileId, emoji, setName, description)
- Fuzzy search by description, emoji, and set name
- Persist to ~/.clawdbot/telegram/sticker-cache.json

Config:
- Single `channels.telegram.actions.sticker` option enables both
  send and search actions

🤖 AI-assisted: Built with Claude Code (claude-opus-4-5)
Testing: Fully tested - unit tests pass, live tested on dev gateway
The contributor understands and has reviewed all code changes.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/config/zod-schema.providers-core.ts

@@ -128,6 +128,7 @@ export const TelegramAccountSchemaBase = z
         reactions: z.boolean().optional(),
         sendMessage: z.boolean().optional(),
         deleteMessage: z.boolean().optional(),
+        sticker: z.boolean().optional(),
       })
       .strict()
       .optional(),