fix(identity): resolve KycTier merge markers + style: cargo fmt --all

[nanaf6203-bit]

What

• Resolve the unresolved git conflict markers in contracts/identity/lib.rs (the KycTier enum, lines 227-244) by picking the main side, preserving both 5-variant CamelCase naming (Tier3Enhanced) AND 5-variant underscored naming (Tier3_Enhanced). Both forms are already in active use throughout the rest of the file (complete_kyc_verification matches both, tests reference both, initialize_kyc_tiers initializes as CamelCase).
• Apply cargo fmt --all to the workspace (21 files, ~742 +/- 708).

Why

KycTier carried conflict markers from PR #547 (7b283b86) that was squash-merged into main, which had been blocking the new smoke.yml cargo fmt --check step from running on main.

Heads-up: cargo fmt --check is still red on this tree

I did not auto-merge this PR. A separate structural issue in the workspace layout prevents cargo fmt --all -- --check from exiting 0 even with this PR applied:

• contracts/insurance/src/lib.rs declares mod premium_engine; inside #[ink::contract] mod propchain_insurance { ... }, so the compiler looks for src/propchain_insurance/premium_engine.rs. The .rs file is currently at flat src/premium_engine.rs.
• Same pattern in contracts/tax-compliance/src/lib.rs: mod tax_engine;, mod jurisdiction_presets;, mod tax_strategies; declared inside mod tax_compliance { ... }, files at flat src/. Compiler looks for src/tax_compliance/{tax_engine,jurisdiction_presets,tax_strategies}.rs.

Required follow-up (separate PR): git mv the four flat .rs files into the expected subdirectories, plus a handful of caller-path updates (payments.rs uses crate::tax_engine, which becomes crate::tax_compliance::tax_engine after the move; compliance.rs and optimization.rs likewise).

Scope

Path	Diff
contracts/identity/lib.rs	conflict markers resolved to main-side 10-variant list
20 other files	cargo fmt --all auto-format only

Branch: fix/cargo-fmt-post-smoke
Base: main
Diff stat: 21 files, +742/-708