feat(auth): add builder-api-key management (create/fetch/revoke)

[naruto11eth]

Ports the ts-sdk /auth/builder-api-key surface to the secure clients (DEV-153 / #51).

• create_builder_api_key() / fetch_builder_api_keys() — authenticate as the account (L2 via secure_clob). create returns the BuilderApiKey credential; fetch returns BuilderApiKeyInfo records (key, created_at, revoked_at).
• revoke_builder_api_key() — authenticated by the builder key's own HMAC (POLY_BUILDER_*), per ts-sdk#68 (working-as-intended), not account L2. Raises UserInputError unless the client holds the builder key to revoke.
• Extracts a shared build_builder_key_headers so builder-key HMAC header construction has a single source of truth (the relayer resolvers now reuse it).

Sync + async parity. Unit tests cover the parsers and client methods, including a guardrail that revoke carries POLY_BUILDER_* and not account L2.

Naming: adds BuilderApiKeyInfo for the list record (additive — no breaking change); BuilderApiKey stays the credential. A pre-1.0 rename to mirror ts-sdk's BuilderApiKeyCreds/BuilderApiKey split is deferred.

Follow-up: a live @metered create→fetch→revoke round-trip (needs real builder credentials) is intentionally not included here — it's the only check that confirms the server's exact signed inputs.

Refs DEV-153, #51

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Note

Medium Risk
Touches credential lifecycle and HMAC auth paths; revoke’s builder-key-only signing is security-sensitive but aligned with ts-sdk and covered by tests.

Overview
Adds /auth/builder-api-key support on sync and async secure clients: create and list use account L2 (secure_clob); revoke uses the builder key’s own POLY_BUILDER_* HMAC on clob, not L2, and raises UserInputError unless the client was created with that BuilderApiKey.

Introduces BuilderApiKeyInfo for list rows (key, created_at, revoked_at) and centralizes builder-key signing in build_builder_key_headers, reused by relayer resolvers and revoke. Response parsers and unit tests cover auth shapes and the revoke header guardrail.

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