* docs(platforms): add HTTP Bot adapter tutorial (zh/en/ja)
Server-to-server HTTP integration guide for the new http_bot platform
adapter: signed inbound webhook, signed outbound callbacks, N->1 aggregation,
1->M multi-reply, session reset, sync convenience mode, error codes, and a
5-minute reference-client demo. Registered in docs.json nav for all three
locales; adds the platform icon.
* docs(http-bot): link the interactive playground in all locales
Add a section pointing at examples/http-bot/playground.py (browser debug
console: sign -> POST -> 202 -> live callbacks) ahead of the CLI reference
clients, in zh/en/ja.
* style(platforms): use </> code icon for http-bot logo
