feat: add HTTP CONNECT proxy support for Telegram and Claude API

Enable ESP32-S3 to reach api.telegram.org and api.anthropic.com through
an HTTP CONNECT proxy (e.g. Clash Verge), required in regions where
these services are blocked.

- New proxy module (http_proxy.c/h): CONNECT tunnel + TLS via esp_tls
  with pre-connected socket injection (esp_tls_set_conn_sockfd)
- Telegram and LLM modules split into direct/proxy paths
- CLI commands: set_proxy <host> <port>, clear_proxy
- Proxy config persisted in NVS
- Fix TLS buffer: MBEDTLS_SSL_IN_CONTENT_LEN 4096 → 16384
- Increase task stacks for TLS overhead (poll 12KB, agent 12KB, outbound 8KB)
- Default model changed to claude-opus-4-6
- Capture raw error body for non-200 API responses

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

main/CMakeLists.txt

@@ -12,6 +12,7 @@ idf_component_register(
         "gateway/ws_server.c"
         "cli/serial_cli.c"
         "ota/ota_manager.c"
+        "proxy/http_proxy.c"
     INCLUDE_DIRS
         "."
     REQUIRES