Cover HIPAA §(J) account numbers; split hipaa.rs by posture

[martsokha]

Summary

Before this change HIPAA Safe Harbor / Limited Data Set / Expert Determination scoped `bank_account` alone under `§(J)`. Real `§(J)` — "account numbers" per `§164.514(b)(2)(i)(J)` and `§164.514(e)(2)(x)` — covers every individual-linked account identifier the pattern set detects: also `iban`, `payment_card`, and (under the `§(R)` catch-all reading) `crypto_address`.

That's why the customer-onboarding CSV under HIPAA Expert Determination silently left IBAN, credit-card, and crypto values untouched.

API

Adds a `HipaaAccountNumbers` enum on `PolicyTemplate::HipaaDeidentification`:

• `Standard` (default): `bank_account` + `iban` + `payment_card`. The traditional `§(J)` reading; matches every de-ID vendor's Safe Harbor preset.
• `Extended`: adds `crypto_address`. Deployments where wallet addresses can appear in patient-facing artifacts opt in.

Both tiers apply uniformly across Safe Harbor, LDS, and Expert Determination — `§(J)` scope is a property of the identifier list, not the removal method. Threaded through `hipaa::template()` and the three per-method builders. `accounts` is `#[serde(default)]`, so callers already sending `{"method": "safe_harbor"}` continue to work.

Research

HHS OCR's 2012 guidance doesn't narrow "account numbers"; in practice covered entities and de-ID vendors (AWS Comprehend Medical, Google Cloud DLP, etc.) treat bank accounts + IBAN + payment cards as the core §(J) set. The reg does NOT sanction a "Basic vs Extended" split within the four labels themselves — every account identifier is a removable §(J) item — but there IS meaningful ambiguity around crypto wallets (a newer instrument that the reg reads via §(R) catch-all), which is exactly what `Standard` vs `Extended` splits.

Folder split

While in there, split the 800-line `hipaa.rs` into a `hipaa/` folder:

• `mod.rs` — module doc, `HipaaDeidMethod`, `HipaaAccountNumbers` re-export, `EFFECTIVE_DATE`, `template()` dispatch, all 10 tests
• `account_numbers.rs` — `HipaaAccountNumbers` enum + label constants + impl
• `safe_harbor.rs`, `limited_data_set.rs`, `expert_determination.rs` — one posture per file, each owning its own constants and UUIDs

Each posture owns its own labels; Expert Determination reaches into `safe_harbor` for the shared 18-identifier label set.

New tests

• `standard_accounts_cover_the_traditional_section_j_set`
• `extended_accounts_add_crypto_to_the_standard_set`
• `account_tier_lands_in_every_hipaa_method`

Test plan

• `cargo fmt --all --check`
• `cargo clippy --workspace --all-features --all-targets -- -D warnings`
• `cargo test --workspace --all-features --all-targets` (33 template tests pass)
• `RUSTDOCFLAGS=-D warnings cargo doc --workspace --all-features --no-deps`
• `cargo machete`

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