fix: release QA hardening across processing, media, security, and CI gates (#649)

A release-readiness QA pass over the whole product. The commits split into
defects a user would hit and gates that were reporting green while measuring
nothing.

## Fixes that change behaviour

Rate limiting was bypassable on every install: TRUST_PROXY defaulted to true, so
request.ip came from a client-set header and a forged X-Forwarded-For got past
the login limiter. The default is now a private-network trust list.

A transient Postgres outage stranded in-flight jobs, leaving finished output on
disk with no row pointing at it. A reconciler now resolves those rows and adopts
the bytes rather than dropping the work.

A Redis connection that moved to a new address wedged every read-blocked
consumer, so completions stopped signalling while health still answered 200.
Socket timeouts plus subscriber pings recover it.

Installing more than one AI bundle left the shared venv multi-versioned and
silently broke three tools. The installer now reconciles distributions to one
version each.

Converting an image to JXL at quality 1 through 4 returned a 500, because
libjxl 0.7 rejects the distance those values compute. The quality is floored at
what the encoder honours. A missing ffmpeg was also reported to the user as a
corrupt upload; it now says the engine is unavailable.

RAW uploads reached an unpatched LibRaw on arm64, so it is built from source at
0.22.2, and the release scan was split so it can fail on an unfixed critical
instead of hiding it behind ignore-unfixed.

## Gates that could not fail

Two mutation lanes ran zero mutants because Stryker crawled the gitignored docs
build; coverage discarded its whole report on any failing test; the lint gate
skipped root tests, scripts, and two workspaces; and several generated matrices
counted a host missing ffmpeg as a passing tool. Each now measures what it
claims.

Full evidence and the outstanding release items are tracked locally and are not
part of this branch.

apps/docs/zh-CN/guide/users-roles.md

@@ -1,8 +1,9 @@
 ---
 description: "在 SnapOtter 中管理用户、内置角色与自定义角色、权限、API 密钥、团队、会话以及审计日志。"
-i18n_source_hash: 5e28af686c96
+i18n_source_hash: bea8955f3aff
 i18n_provenance: human
-i18n_output_hash: db9aecb6141c
+i18n_output_hash: 586307e9d95e
+i18n_hash_version: 2
 ---
 
 # 用户、角色与权限 {#users-roles-permissions}
@@ -82,12 +83,12 @@ SnapOtter 包含三个内置角色。它们无法被修改或删除。
 | `pipelines:all` | 查看和管理所有用户的流水线 |
 | `settings:read` | 查看实例设置 |
 | `settings:write` | 修改实例设置 |
-| `users:manage` | 创建、更新和删除用户账户 |
+| `users:manage` | 在参与者的权限范围内创建和管理用户帐户 |
 | `teams:manage` | 创建、更新和删除团队 |
 | `features:manage` | 安装和管理 AI 功能包 |
 | `system:health` | 访问健康与就绪端点 |
 | `audit:read` | 查看审计日志并列出角色 |
-| `compliance:manage` | 管理 GDPR 生命周期和合规功能 |
+| `compliance:manage` | 管理 GDPR 生命周期和合规性功能；破坏性用户操作仍受权限限制 |
 | `webhooks:manage` | 配置出站 webhook |
 | `security:manage` | 管理安全设置（IP 允许列表、SSO 强制） |
 
@@ -110,15 +111,17 @@ curl -X POST http://localhost:1349/api/v1/roles \
 
 角色名称必须为 2 到 30 个字符，小写字母数字，可包含连字符和下划线。
 
-### 管理员保留权限 {#admin-reserved-permissions}
+### 委派管理边界 {#delegated-administration-boundaries}
 
-有三项权限保留给内置角色，无法分配给自定义角色：
+所有 17 个权限都可以通过自定义角色委派，但管理权限并不会使该角色等同于内置 `admin` 角色。 `users:manage`授权的用户突变、`compliance:manage`授权的破坏性操作以及`security:manage`授权的自定义角色管理均受参与者当前权限的约束：
 
-- `compliance:manage`
-- `webhooks:manage`
-- `security:manage`
+- 内置角色遵循`admin` > `editor` > `user`；自定义角色位于内置角色下方。
+- 目标的权限必须包含在参与者的**有效**权限中。因此，限定范围的 API 密钥无法行使其范围中省略的权限。
+- 目标角色的工具访问权限必须包含在参与者自己的工具访问权限中。
+- 当角色记录为 `disabled:<original-role>` 时，已禁用的帐户将根据其原始角色进行检查。
+- 删除自定义角色还需要分配内置`user`后备的权限；禁用的成员仍然禁用为 `disabled:user`。
 
-角色 API 会拒绝任何包含这些权限的请求。只有内置的 `admin` 角色才能访问它们。
+全局凭证和配置更加严格：颁发或撤销 SCIM 令牌以及导入实例配置需要具有完整有效管理权限的内置 `admin` 角色。
 
 ### 工具级权限 {#tool-level-permissions}