feat(protocol2): website account provisioning & unlinking (Part A)

Adds the account-provisioning plane from docs/PROTOCOL_2.md Part A: the
website can create game accounts and unlink them, gated by a shard-wide
signup mode. The existing [link flow is unchanged.

Overlay:
- BridgeConfig: SignupMode (website|game|hybrid, default hybrid; unrecognized
  falls back to game), AccountCreateEnabled (mode-following default),
  RequireIpForCreate, name/password caps, and a boot warning when the core
  Accounts.AutoCreateAccounts setting contradicts the mode.
- BridgeAccounts (new): account.create (mode gate, actor required, char-safety
  mirrored from AccountHandler, collision check, per-IP cap via CanCreate/
  LogAccess with fail-closed missing/loopback IP, create + WebsiteUserId link,
  account.audit; password never logged or echoed) and account.unlink (Owner
  floor via BridgeAdmin.Protected, clears the tag).
- BridgeAccountLink: in-game [unlink command, emits account.unlinked.
- BridgeAdmin: Protected / ResolveTargetAccount promoted to public for reuse.

Sidecar:
- POST /accounts/create, DELETE /link/:account, respond_account status mapping
  (409 collision / 429 ip cap / 403 disabled|protected / 404 not-linked / 400).
- store.record_unlink drops the mirrored link row.
- PROTOCOL_VERSION -> 2 (outbound events additive; new endpoints need v2).

Docs: INTEGRATION.md protocol bump, account.* events, endpoints, 409/429;
PROTOCOL_2.md Part A marked built.

Verified: sidecar cargo check clean; overlay compiles in the full ServUO
Scripts tree (0 errors, 0 warnings). Live end-to-end run still pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sidecar/src/main.rs

@@ -20,7 +20,11 @@ use tracing_subscriber::EnvFilter;
 /// Wire-protocol version between the website and the sidecar. Bump this whenever an event or
 /// endpoint's shape changes so a mismatched client is detected immediately (409 / health) instead
 /// of failing in confusing ways.
-pub const PROTOCOL_VERSION: u32 = 1;
+///
+/// v2 (Protocol 2.0): adds the account-provisioning verbs/endpoints (`POST /accounts/create`,
+/// `DELETE /link/:account`) and their events. Outbound event kinds are additive, so a v1 website
+/// keeps working against the live feed; the new *endpoints* require a v2 sidecar.
+pub const PROTOCOL_VERSION: u32 = 2;
 
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {