fix(search): restore privacy kind exclusions at the FTS storage layer

The Typesense→Postgres FTS rewrite replaced out-of-band indexing with
`search_tsv TSVECTOR GENERATED ALWAYS AS (to_tsvector('simple', content))
STORED` over every row. The old relay (handlers/event.rs:287 on main)
deliberately skipped search-indexing for three kind classes, and the new
search query layer has no kind exclusion — so gift wraps, DM-visibility
snapshots, and event reminders were all in the FTS index.

Fix at the storage layer (option A — single source of truth, zero
app-layer drift across multiple search call sites): make the generated
column yield `NULL::tsvector` for excluded kinds via a CASE expression.
A NULL tsvector never matches `@@`, so excluded rows are structurally
unsearchable.

Excluded set, parity with main's `handlers/event.rs:287-290`:
- 1059  KIND_GIFT_WRAP        (NIP-17 ciphertext)
- 30300 KIND_EVENT_REMINDER   (AUTHOR_ONLY_KINDS — defense in depth)
- 30622 KIND_DM_VISIBILITY    (per-viewer private hide state)

Constants are inlined in the migration with a comment naming the
`buzz_core::kind` names: sqlx migrations are frozen SQL and can't
`use buzz_core::kind`; importing core into a migration would be worse
drift than the inline-with-comment shape.

Three coupled layers:

1. Schema CASE in migrations/0001_initial_schema.sql. The 0001 schema
   was consolidated by Max in 4b7654a1c (Lane-0 contract) and is
   pre-deploy; editing in place rather than adding a new migration
   matches the agreed shape and is covered by
   `run_migrations_applies_consolidated_initial_schema_on_fresh_database`.

2. buzz-search/tests/fts_integration.rs — new test
   `excluded_kinds_are_storage_level_unsearchable` inserts kind:1059 +
   kind:30300 + kind:30622 + kind:9 with the same unique token; asserts
   only the kind:9 control surfaces. Each excluded kind has its own
   load-bearing negative assertion with a diagnostic message naming the
   regression, plus a tight exactly-one-hit bound.

   Mutate-bite verified: dropping the CASE's NULL branch (revert to
   `to_tsvector('simple', content)`) makes excluded kinds searchable
   and the test fails RED with the designed message
   "kind:1059 MUST NOT be searchable — privacy regression in search_tsv
   generated column". Restored → 10/10 green.

3. crates/buzz-test-client/tests/e2e_nostr_interop.rs — rewrote
   `test_nip17_gift_wrap_not_searchable` to use the relay's actual
   NIP-50 search seam (`Filter::new().search(token)`,
   `collect_until_eose`) instead of the now-removed Typesense
   `/multi_search`. Pattern cribbed from
   `test_nip50_search_returns_results_and_eose`. Pointer comment to
   the underlying mutate-bite in fts_integration.rs.

Verification on `quinn/search-kind-exclusions` off `34ffb8ab3`:
- `cargo test -p buzz-search --tests -- --include-ignored`: 10/10
- `cargo test -p buzz-db -- --include-ignored`: 99/99 (incl. migration
  lints + consolidated-schema fresh-DB)
- `cargo check -p buzz-test-client --tests`: clean
- `cargo clippy -p buzz-search -p buzz-db --all-targets -- -D warnings`:
  clean
- `cargo fmt --all -- --check`: clean

Co-authored-by: Tyler Longwell <tlongwell@block.xyz>
Signed-off-by: Tyler Longwell <tlongwell@block.xyz>

migrations/0001_initial_schema.sql

@@ -203,7 +203,23 @@ CREATE TABLE events (
     -- community-leading btree filters BitmapAnd-ed with the GIN probe, so the
     -- GIN index itself stays the minimal `GIN (search_tsv)` (Max's caveat:
     -- avoid btree_gin unless EXPLAIN proves it buys something).
-    search_tsv  TSVECTOR GENERATED ALWAYS AS (to_tsvector('simple', content)) STORED,
+    --
+    -- Privacy kind exclusions (parity with the pre-rewrite Typesense feed —
+    -- old relay's `handlers/event.rs:287-290` skip set):
+    --   1059   = KIND_GIFT_WRAP        (NIP-17 ciphertext)
+    --   30300  = KIND_EVENT_REMINDER   (AUTHOR_ONLY_KINDS — defense in depth)
+    --   30622  = KIND_DM_VISIBILITY    (per-viewer private hide state)
+    -- NULL tsvector never matches `@@`, so excluded rows are storage-level
+    -- unsearchable. Constants kept in `buzz_core::kind` (KIND_GIFT_WRAP,
+    -- KIND_EVENT_REMINDER, KIND_DM_VISIBILITY); inlined here because a sqlx
+    -- migration is frozen SQL and cannot import the Rust constant. If a new
+    -- privacy-sensitive kind is added there, update this list and add a
+    -- regression test in `buzz-search/tests/fts_integration.rs`.
+    search_tsv  TSVECTOR GENERATED ALWAYS AS (
+        CASE WHEN kind IN (1059, 30300, 30622) THEN NULL::tsvector
+             ELSE to_tsvector('simple', content)
+        END
+    ) STORED,
     sig         BYTEA NOT NULL,
     received_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     channel_id  UUID,