[core] Support REST catalog branch management

[JingsongLi]

Purpose

PyPaimon already supports REST branch creation, listing, deletion and fast-forward. Add the missing Rust Catalog, RESTApi and Native binding capabilities, following Java's RESTCatalog and RESTApi contracts.

Changes

• Add Catalog::{create_branch, drop_branch, fast_forward, list_branches} with unsupported defaults and a REST implementation. Use Java's endpoints, branch/fromTag payload, empty forward request, nullable branch-list response, ordering and operation-specific errors.
• Expose thin PaimonCatalog methods that accept string/tuple identifiers and release the GIL. config_required=False reuses resolved REST configuration without fetching /config again.
• Provide structured CatalogError fields so PyPaimon can retain its public exception types. Preserve missing JSON status codes, unknown HTTP errors and transport errors; keep ForkSafetyError distinct.
• Reject empty/dot path components before dispatch. Keep publication on the REST server without shared-data cleanup or replay through another backend.
• Implement OpenAPI V4 (ACS4-HMAC-SHA256) in Rust core, selected by dlf.signing-algorithm=openapi-v4. Port Java's canonical request, RFC 3986 query encoding, payload hash, credential scope and 61 action mappings. Existing signing algorithms remain available.
• Merge generated authentication headers case-insensitively and replace JSON Content-Type defaults rather than append duplicate values.
• Accept arbitrary successful mutation response bodies. Retry only GET on 429/503, with at most five retries and Java's Retry-After/backoff behavior; do not status-retry POST/DELETE.
• Align connection/read timeouts with Java's three-minute defaults instead of a 30-second total request deadline.

Verification

• Rust API unit tests: 104 passed.
• REST API/catalog/branch integration tests: 188 passed.
• Binding catalog/branch/GIL/table tests: 83 passed.
• PyPaimon Native branch/lifecycle tests against this binding: 109 passed, exercising 161 plans, 162 reads, 140 writes and 84 commits.
• Ordinary PyPaimon branch/DTO/DLF signer tests: 82 passed.
• Rust 1.98.0 Clippy for core and bindings with all targets and -D warnings, rustfmt, changed-file flake8 and git diff --check: passed.
• A real HTTP mutation with a 31-second response delay succeeded after one request, validating removal of the old total deadline.

Repeated independent review and regression testing covered Java parity, V4 signatures, credential caching/refresh, header collisions, GET retries, transport errors and uncertain publication. V4 integration independently recomputes wire MACs with the Python signer while guarding against Python operation fallback. Paimon REST authenticates each request; no cross-client cookie/session synchronization or response observation API is introduced.

PyPaimon's mock server acknowledges fast-forward; request semantics are verified against Java and Rust protocol tests. This does not claim to test a production server's snapshot-switching implementation.

[leaves12138]

LGTM