Introduce `anyllm_client` crate containing HTTP client construction,
SSRF-safe DNS resolver, retry/backoff logic, rate limit header parsing,
and SSE frame parsing. These were previously inlined in the proxy crate.
Rename crates from `anthropic_openai_proxy`/`anthropic_openai_translate`
to `anyllm_proxy`/`anyllm_translate` throughout.
proxy/backend: now re-exports retry, rate limit, and SSE symbols from
the client crate; `send_with_retry` and `build_http_client` are thin
adapters bridging BackendAuth/TlsConfig to the client crate's types.
streaming: remove duplicate `find_double_newline` and
`MAX_SSE_BUFFER_SIZE` definitions; import from `crate::backend` instead.
Fix missing `pub mod` declarations in translator and proxy that were
accidentally replaced by doc comments (streaming, usage_map, server,
redact).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>