feat(auth)!: go fully passwordless and fix cross-check review findings

Remove password authentication everywhere; the only session doors are
passkey (WebAuthn), email OTP, in-game bind codes, QR scan-login, and
op-login vouching. Remediates the 33-finding cross-check review across
backend, CLI, panel, plugins, and docs.

Backend/CLI:
- Drop password routes and fields from account/user/onboard/auth
  handlers; align tests (new account subtests, naming reserves
  "console", op-login/onboard/qr-login test updates).
- Add migrations 0016_op_login.sql and 0017_drop_password.sql.
- Thread panel/admin hostnames from hostcfg through api.go,
  setup_panel.go, tui_root.go and tui_preflight.go instead of
  hardcoding; bootstrap.sh writes panel-hostname/admin-hostname
  into felis.toml.
- Reword breakglass and TUI copy for passwordless flows.

Panel:
- Delete the ChangePassword page and all password UI; align
  login/auth/api/types with the passwordless contract; add the
  migration and op-login approval flows.
- i18n: convert ImageBuildPage durations/status badges and
  ServerLuckPerms strings to translation keys; drop 72 orphan keys
  per locale; unify the title as "Felis - Console".

Plugins (all six rebuilt):
- Velocity waiting router returns 503 at_capacity during wake;
  MOTD/control-channel copy and config comments.
- Paper zh menu title; Limbo bind-code TTL 600s with panel_url
  preference; unified /link lines in fabric/forge/neoforge; shared
  link-client javadoc contract fixes.

Docs: openapi.yaml, sequence-diagrams.md, deploy/limbo/README.md and
plugins/README.md aligned with the implementation.

BREAKING CHANGE: migration 0017 irreversibly drops
users.password_hash and users.must_change_password; password login
cannot be restored after migrating.

docs/sequence-diagrams.md

@@ -120,10 +120,10 @@ sequenceDiagram
     Game->>Game: read verified online-mode UUID
     Game->>LinkClient: requestCode(mc_uuid)
     LinkClient->>APIInternal: POST /api/v1/internal/account/link/code {mc_uuid}
-    APIInternal->>APIInternal: validate UUID; default auth_source=mojang if absent; generate 8-symbol code
+    APIInternal->>APIInternal: validate UUID; derive auth_source from the UUID version nibble if absent (v3 → thirdparty, else mojang); generate 8-symbol code
     APIInternal->>Repo: CreateLinkCode(code, mc_uuid, auth_source, expires_at)
     Repo-->>APIInternal: inserted account_link_codes row
-    APIInternal-->>LinkClient: 201 {code, expires_at}
+    APIInternal-->>LinkClient: 201 {code, expires_at, panel_url?}
     LinkClient-->>Game: LinkCode
     Game-->>Player: show one-time code in chat