feat(history): add get_history_page_with_meta pagination metadata (#380)

[ebenezershadrack123-star]

Summary

Closes #380.

Adds a metadata-carrying companion get_history_page_with_meta that returns a
HistoryPage { items, total, has_more } so consumers can detect end-of-history
and the total size in a single read — without a separate get_history or
get_retention_limit call.

Changes

• apexchainx_calculator/src/lib.rs — new #[contracttype] HistoryPage
  struct; new #[contractimpl] get_history_page_with_meta method; registered
  the method in get_public_api.
• apexchainx_calculator/src/history.rs — mirrored delegated
  get_history_page_with_meta implementation (kept in lockstep with the
  contract entry point, per the existing pattern).
• apexchainx_calculator/src/tests.rs — 6 tests covering total/has_more,
  empty history, offset-beyond-end, zero-limit, byte-for-byte parity with
  get_history_page, and saturating arithmetic; bumped the public-API method
  count 57 → 58.
• Docs — CHANGELOG, README, HISTORY_PAGINATION_POLICY, API_STABILITY_SCORECARD,
  MODULE_OWNERSHIP, CONTRACT_MAINTENANCE_POLICY, PROJECT_CONTEXT.

Semantics

• items is identical to get_history_page(offset, limit).
• total is the full history length at read time.
• has_more is true exactly when min(saturating_add(offset, limit), total) < total.
• get_history_page is unchanged (backward compatible).
• Read-only: no storage writes, no events, no auth.

Acceptance criteria

• get_history_page_with_meta returns pagination metadata including total and has_more
• Existing get_history_page behavior is unchanged
• Tests verify correct metadata for various offset/limit combinations

Verification

cd apexchainx_calculator
cargo fmt --check
cargo clippy --all-targets -- -D warnings
cargo test --lib          # 575 passed, 0 failed (1 pre-existing slow stress test skipped)
cargo check --target wasm32-unknown-unknown --lib

Type of Change

• New feature
• Bug fix
• Breaking change
• Documentation update

Related Issue

Closes #380