chore(db): drop Phase-A NIP-FI relay-side authority ledger (#7221)

Removes the dead relay-side authority ledger introduced by migrations
0041 and 0042, and the dead `require_attested_key` verifier knob from
`buzz-auth`. Both are unreachable by design under NIP-FI spec v2 (#7214,
squash `d4420eb47`), which makes OSS Buzz stateless for identity: the
relay neither stores nor verifies an authority chain.

## What changes

**`migrations/0044_drop_nip_fi_ledger.sql`**
Drops all fifteen NIP-FI ledger tables and their trigger functions using
`CASCADE` to resolve the circular deferred FK between
`identity_bindings` and `identity_lifecycle_history`. Drops proceed in
FK dependency order: selectors → history/bindings →
enrollment_policies/receipts → parallel drop of auth tables. Restores
`community_write_fence_excluded_table` to its pre-0041 body (removes
NIP-FI table names from the exclusion array).

**`schema/schema.sql`**
Removes the NIP-FI section (~1885 lines of tables, functions, and
triggers) and updates `community_write_fence_excluded_table` to match.

**`crates/buzz-db/src/runtime/migration.rs`**
- Updates the `embedded_migrator_contains_consolidated_initial_schema`
sanity check: count 43→44, adds 0044 assertion block (verifies `DROP
TABLE` statements and absence of NIP-FI names from `schema.sql`).
- Removes ~2580 lines of NIP-FI Postgres integration tests (all
`#[tokio::test] #[ignore = "requires Postgres"]` from the 0041/0042
behavioral coverage).
- Removes the `extract_excluded_table_array` drift check (0042 body no
longer matches `schema.sql` by design).
- Adds `migration_0044_drops_populated_nip_fi_ledger_cleanly`: runs
migrations to 0042, seeds rows in `authorization_operation_receipts` and
`authorization_invalidation_domains`, then runs to 0044 and verifies all
fifteen NIP-FI tables are absent.

**`crates/buzz-auth/src/nip_fi/config.rs`**
Removes `require_attested_key: bool` from `IssuerPolicy` — field,
constructor parameter, accessor, and its contribution to
`derive_assertion_policy_id`.

**`crates/buzz-auth/src/nip_fi/verifier.rs`**
`parse_nostr_pubkey_claim` no longer takes a `policy` parameter. The
`None` (absent claim) arm now returns
`Err(VerifierError::ClaimRejected)` unconditionally instead of
conditionally on `policy.require_attested_key()`.

**`crates/buzz-auth/src/nip_fi/verifier/tests.rs`**
- Removes `missing_nostr_pubkey_denies_under_attested_key_policy` (the
sole `require_attested_key: true` call site).
- Removes `false,` from all eleven `IssuerPolicy::new` call sites.
- Injects `nostr_pubkey` by default in `mint_signed_by` (spec v2
requires it unconditionally).
- Updates `valid_access_token_verifies` to assert
`asserted_key().is_some()`.

**`crates/buzz-auth/src/nip_fi/startup/tests.rs` + `jwks/tests.rs`**
Removes `false,` from all `IssuerPolicy::new` call sites and adds
`nostr_pubkey` to all token-minting helpers.

## Verification

- Fresh-DB migration run to head: all migrations apply cleanly in
sequence.
- Populated-0041/0042-DB migration through 0044: seeds rows in live
NIP-FI tables, verifies all fifteen are dropped without error.

Closes the dead-code inventory item from the spec-v2 cleanup plan
(channel `48374f48`). Follows #7214.

---------

Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: Duncan <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
Co-authored-by: Duncan <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>

docs/nips/NIP-FI.md

@@ -155,11 +155,8 @@ single-issuer deployment is a registry of length one.  [FI-TRACE-CROSS-DOMAIN-CO
 
 The existing `FederatedAssertionVerifier<S>` and `ProductionJwksSource<F>`
 (merged in PR 3 / `70895b355`) implement the verification procedure described
-here.  The `require_attested_key` flag in `IssuerPolicy` is the per-issuer
-enforcement primitive for the unconditional `nostr_pubkey` requirement in this
-section; conformance to NIP-FI v2 requires startup validation that forces this
-flag true for every configured issuer.  That integration is a follow-on code
-change outside this PR.
+here.  The `nostr_pubkey` claim is unconditionally required — absence rejects
+regardless of issuer policy (NIP-FI v2, PR #7221).
 
 ### JWKS snapshot
 
@@ -402,8 +399,7 @@ Any failure at any step is fail-closed: no side effects occur and the relay
 returns the appropriate error.
 
 This verifier and the disconnect API endpoint are follow-on code changes
-outside this PR, in the same way that the `require_attested_key` enforcement
-integration is.
+outside this PR.
 
 ### Request