feat(safety): report, block and hide chat lines (MODULE_API 1.21.0)

USER_SAFETY.md step 3, the module half of report, block and hide.

- server/safety.js registers the rust.chat report target (snapshot for one
  reader, null when they could not have seen the line; staff's hide and
  unhide) and the steam game identity (ownersOf from rust_account_links).
- The events feed filters chat per reader, in the query: lines from a
  blocked account's Steam ids, the reader's unlinked Steam-ID blocks and the
  lines they hid. Signed-in readers get canBlock on each chat line (false for
  their own and for staff-linked players). Lines staff hid for everyone are
  left out for everyone but staff, who get them with hidden: true.
- rust_events gains hidden_at and hidden_by (ALTER ... IF NOT EXISTS).
- POST /admin/rust/chat/:id/hide and /unhide (admin, moderator), logged.
- The feed's chat lines get a menu: Report, Hide for me, Block player,
  and for staff Hide for everyone / Show to everyone again.
- coreApi ^1.21.0; ci/core-ref.json pinned to the website#233 merge;
  routes.manifest.json and swagger-fragment.json regenerated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/db/schema.sql

@@ -246,6 +246,18 @@ CREATE TABLE IF NOT EXISTS rust_events (
   KEY idx_rust_events_created (created_at)
 );
 
+-- Staff's "Hide for everyone" on a chat line (USER_SAFETY.md §4.2, S10). Set from
+-- core's Reports queue or from the line's own menu, and cleared from that menu.
+-- A hidden line is left out of the feed for everybody but staff, who still get it,
+-- marked, so a hide can be checked and undone where it lives. The row is kept, and
+-- the retention sweep prunes it like any other.
+--
+-- `hidden_by` is the staff account's id, with no foreign key: the hide stays a
+-- hide when the account that made it is deleted, and nothing reads it back as a
+-- person. ALTER rather than columns above, so an existing install gets them too.
+ALTER TABLE rust_events ADD COLUMN IF NOT EXISTS hidden_at DATETIME NULL;
+ALTER TABLE rust_events ADD COLUMN IF NOT EXISTS hidden_by INT NULL;
+
 
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