feat(shard)!: declare wire protocol 3

The site's declared version is the admin-set uo_link_config.protocol column, so
the sidecar's PROTOCOL_VERSION 2 -> 3 bump has to be matched here or every REST
call 409s and uoLinkSocket closes the WS on the ws.hello mismatch. Five places
carry the number and all five move together: the column default, the model's
DEFAULT_PROTOCOL (what a site with nothing saved yet declares), the two
`config.protocol || 1` fallbacks in uoLinkClient/uoLinkSocket -- unreachable
today, but an unset value quietly sending 1 is exactly the confusing 409 the
version check exists to prevent -- the admin form's initial value, and the
documented env default.

The boot migration is the only subtle part. schema.sql is re-run on EVERY boot,
and `protocol` is admin-editable, so a bare UPDATE would silently un-pin an
operator who had deliberately pinned an older sidecar in Admin -> Shard. It is
therefore gated on a marker row in `settings`, written after the UPDATE: the
first boot on this build migrates, every later boot is a no-op. `protocol < 3`
rather than `= 2` picks up an install still on the old default of 1, which could
not have been talking to a v2 sidecar anyway. A fresh install has no row to
update and just gets the marker plus the new column default.

Verified against the local MariaDB through ensureSchema (the production path):
2 -> 3 with the marker written and the column default now 3; pinned back to 2 by
hand, re-ran, and it STAYED 2 -- the one-shot property holds. 673 server tests,
47 client tests, client build green.

Co-Authored-By: Claude <noreply@anthropic.com>

server/db/schema.sql

@@ -359,7 +359,7 @@ CREATE TABLE IF NOT EXISTS uo_link_config (
   base_url          VARCHAR(255) NULL,
   ws_url            VARCHAR(255) NULL,
   auth_token_enc    TEXT         NULL,
-  protocol          INT          NOT NULL DEFAULT 1,
+  protocol          INT          NOT NULL DEFAULT 3,
   enabled           TINYINT(1)   NOT NULL DEFAULT 0,
   status            VARCHAR(20)  NOT NULL DEFAULT 'disconnected',
   status_detail     VARCHAR(500) NULL,
@@ -1397,3 +1397,19 @@ ALTER TABLE mobile_refresh_tokens ADD COLUMN IF NOT EXISTS last_used_at DATETIME
 -- trust token. A boolean only — the token is returned over that app→server call
 -- and never persisted here (only its sha256 lands in trusted_devices).
 ALTER TABLE mobile_auth_sessions ADD COLUMN IF NOT EXISTS trust_device TINYINT(1) NOT NULL DEFAULT 0;
+
+-- Protocol 3.0 cutover: this build speaks wire protocol 3 (world.ruleset,
+-- points.board, vendor.listing), so the pinned version an existing install
+-- carries has to move with it — a 2 against a v3 sidecar 409s every REST call
+-- and closes the WS on ws.hello. MODIFY fixes the column default for installs
+-- created before the bump (idempotent, like the other MODIFYs here).
+ALTER TABLE uo_link_config MODIFY COLUMN protocol INT NOT NULL DEFAULT 3;
+-- The row itself is admin-editable, and schema.sql runs on EVERY boot, so this
+-- must be one-shot: an operator who deliberately pins an older sidecar in
+-- Admin → Shard has to stay pinned. The marker row in `settings` is what makes
+-- it fire once — written after the UPDATE, and on a fresh install (no
+-- uo_link_config row yet) it is simply written with nothing to update.
+UPDATE uo_link_config SET protocol = 3
+  WHERE id = 1 AND protocol < 3
+    AND NOT EXISTS (SELECT 1 FROM settings WHERE `key` = 'uo_link_protocol_3_migrated');
+INSERT IGNORE INTO settings (`key`, value) VALUES ('uo_link_protocol_3_migrated', '1');