feat(chart): add relay horizontal autoscaling

[tlongwell-block]

Summary

• replace tauri-plugin-websocket with a small Buzz-owned tokio-tungstenite lifecycle adapter
• isolate each connection behind a bounded queue and cancellable owner task, with native connect/write deadlines and EOF/error cleanup
• add authoritative disconnect / disconnect_all commands and tear down native sockets before Cmd+R reload
• register explicit Tauri ACL permissions and update the browser test bridge

Why

The upstream plugin keeps every writer behind one global mutex, awaits network I/O while holding it, has no force-disconnect command, and can retain native sockets across webview reload. A half-open transport can therefore survive JS reset/reload and block unrelated connections.

This is lifecycle hardening, not a claim that it was the proven root cause of Mat's report: Mat was on 0.4.16 before #2060, and the observed trigger aligns with a relay pod bounce.

Validation

• just ci (Hermit Rust 1.95): pass
• Desktop Tauri suite: 1471 passed, 13 ignored
• Desktop JS suite: 3158 passed
• focused native lifecycle tests: EOF cleanup, bounded/idempotent forced shutdown, cross-connection queue isolation, teardown gate ordering
• independent red-team found three blockers; fixed the TS resurrection-prone approach by dropping ordered per-client awaits, held native connect gate through disconnect_all, and added the inlined-plugin ACL/default permission
• generated ACL confirms websocket:default allows connect/send/disconnect/disconnect_all

Not run

• signed/package release build: requires real bundled sidecar artifacts; compile, clippy, unit, frontend build, and generated ACL all ran locally