polish(token): run localized linter and formatter on token module

[Fayyo]

Closes #500

Ran cargo clippy and cargo fmt on bc-forge-token, fixing all warnings:

lib.rs:

• Added NatSpec doc comments to DataKey variants: Decimals, Name, Symbol, Supply, MaxSupply
• Wrapped code identifiers in backticks in existing doc comments (AdminKey::Admin, AllowanceData)
• Added #[must_use] to read-only public functions (admin, supply, get_max_supply)

rate_limit.rs:

• Wrapped function names in backticks in doc comments (transfer_from, burn_from)

reentrancy_guard.rs:

• Derived Eq on ReentrancyGuardState (already derived PartialEq)
• Made ReentrancyGuard::new const
• Replaced manual if...panic! with assert! in require_not_entered

Verification:

• cargo clippy -p bc-forge-token — 0 warnings
• cargo fmt --check -p bc-forge-token — exit 0
• cargo test -p bc-forge-token — 24/24 pass
• cargo test --workspace — all 136 tests pass

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