docs(adr): 0029 web 界面一律静态 SPA,hub 只出 JSON

记录本次迁移的语义决策:没有 HTTP handler 渲染 HTML;/app 与
/database 是同一个前端工程 filelib-web,构建一次挂两个前缀;
客户端导航用真 URL 路由而非 hash 片段。

两条承重配置约束一并写明:appDir 必须改名(默认 _app 与 admin-web
在根上的 /_app/* 撞重复路由,Fastify 启动即失败),以及
paths.relative=false(同一份 index.html 在不同 URL 深度被送出)。

docs/adr/0029-web-surface-frontend-backend-separation.md

@@ -0,0 +1,132 @@
+# ADR 0029: Web Surfaces Are Static SPAs; the Hub Serves JSON Only
+
+## Status
+
+Accepted.
+
+## Context
+
+The Hub exposes three browser surfaces: the org-admin console (`/admin`), the
+teacher-facing file library (`/app`), and the database admin back office
+(`/database`). They arrived at different times and diverged in how HTML reached
+the browser.
+
+`/admin` and `/app` were already separated: the backend serves a prebuilt static
+`index.html` and never inspects the request; all data flows through JSON
+endpoints. `/database` was not. Roughly 1770 lines across four modules
+(`renderDashboard`/`renderLoginPage` in `routes/databaseRoutes.ts`,
+`routes/adminPanels.ts`, `routes/libraryBrowser.ts`, `routes/libraryPage.ts`)
+assembled HTML template strings server-side, reading the session cookie and
+querying Prisma inside the page handler, with layout expressed as inline
+`style="…"` attributes and behavior as `<script>` text.
+
+A prior migration (`12628c9`) introduced a fourth frontend project,
+`hub/database-admin/`, intended to replace those pages. It was never wired up:
+the concrete route `/database/dashboard` is more specific than the SPA wildcard
+`/database/*`, so the server-rendered handler always won and the SPA's dashboard
+was unreachable. That project's file header claimed the SPA served the dashboard
+and that `/database/config` existed; neither was true. The `npm run build` script
+also never built it, so the `existsSync` guard in `database/static.ts` failed on
+every deploy and the shell was permanently disabled.
+
+Duplicated visual rules were the practical cost: card padding and type sizes were
+restated in each render module, and only the CSS variables in `routes/uiTheme.ts`
+were genuinely shared.
+
+## Decision
+
+**No Hub HTTP handler renders HTML.** Every browser surface is a prebuilt static
+SPA. Page handlers send a byte-identical `index.html` that does not depend on the
+request; all per-user and per-request data is fetched by the client from JSON
+endpoints under `/api/*` or `/database/api/*`.
+
+**`/app` and `/database` are one frontend project, `hub/filelib-web`, built once
+and mounted at two prefixes.** They share the file library browser, the session
+layer, the toast host, and the design tokens; splitting them would duplicate all
+of it. `hub/database-admin` is deleted — superseded before it ever served a
+request.
+
+Two configuration constraints follow from co-hosting two SvelteKit SPAs on one
+Fastify instance, and are load-bearing:
+
+- `filelib-web` sets `appDir: '_filelib'`. The SvelteKit default `_app` collides
+  with the root `/_app/*` asset route that `admin-web` owns
+  (`src/admin/static.ts`); Fastify rejects duplicate routes at startup, so the
+  collision is a boot failure, not a silent misroute.
+- `filelib-web` sets `paths.relative: false`. The same `index.html` is served at
+  different URL depths (`/app`, `/database/dashboard/users`), so relative asset
+  paths would resolve against the wrong base.
+
+**Client-side navigation uses real URL routes, not hash fragments or hidden
+sections.** The six back-office tabs are `/database/dashboard`,
+`/database/dashboard/library`, `/users`, `/groups`, `/search`, `/settings`.
+Refresh preserves position and links are shareable — the previous
+`location.hash` + `display:none` scheme lost both.
+
+Concrete routes must be registered before the SPA wildcards. This is an ordering
+obligation on `database/plugin.ts`, not an incidental detail: the earlier
+`/database/dashboard` shadowing bug is exactly what happens when a concrete page
+route outranks the fallback.
+
+## Consequences
+
+- Authorization is enforced only by the JSON endpoints. A client-side guard (the
+  `isWebsiteAdmin` check in the dashboard layout) is a navigation convenience and
+  carries no security weight; every endpoint keeps its own `fail closed` guard.
+- `/database/api/stats` is a new endpoint carrying what `loadDashboardStats` used
+  to compute inline. It requires silo org `OWNER`/`ADMIN` because it aggregates
+  org-wide counts and the audit stream rather than a per-node permission view.
+- `/database/api/me` grew `displayName` and `avatarUrl`. Anything the old page
+  handler read from Prisma to render chrome has to become part of a JSON payload
+  or it is simply unavailable: the sidebar identity strip showed a raw `userId`
+  until these were added. When migrating a server-rendered surface, the data the
+  template closed over is part of the contract being ported, not an incidental
+  detail of the old implementation.
+- Editing a page no longer requires a Hub restart in development; `vite dev`
+  serves the frontend and proxies data requests to the Hub. In production the
+  `index.html` is cached in memory at startup, so a frontend rebuild does require
+  a restart.
+- Deploy scripts and the silo rate-limit exemption list name `filelib-web` and
+  `/_filelib/*`. Adding a fourth surface means picking another `appDir` and
+  extending that list.
+- The design system is one file, `filelib-web/src/app.css`: an `@theme` block for
+  tokens plus an `@layer components` block for the shared component classes
+  (`.btn`, `.panel`, `.input`, `.select`, `.list`, `.tag`, `.quiet`, …).
+  `routes/uiTheme.ts` is deleted; both halves live there now.
+
+  The first cut of this migration kept only the tokens and restated button,
+  input, and panel styling inline in every component. That reproduced the
+  duplication the old code had — the admin panels visibly regressed — so the
+  component layer was ported too. Components carry layout utilities; they do not
+  restate component styling. The one admitted exception is a data-derived value
+  (tree indent computed from `depth`), which cannot be a static class.
+
+  The icon set (`lib/Icon.svelte`, 13 paths) is likewise shared rather than
+  restated. It came from `adminPanels.ts`; Group nodes deliberately use a
+  two-person silhouette, not a folder glyph, because `MemberGroup` and the file
+  library's `FOLDER`/`PROJECT` are unrelated hierarchies (ADR-0028, ADR-0021).
+
+- **A migrated surface is only done when its endpoint coverage matches.** Two
+  panels were rebuilt from a superficially similar component that predated the
+  migration rather than from the server module they replaced, and the mismatch
+  was invisible in the rendered page:
+
+  - Group management called 5 of 8 endpoints. Rename (`PATCH`),
+    `?includeArchived=1`, `/restore`, and `/users/search` had no entry point, so
+    a soft-deleted group could not be restored through the UI at all even though
+    the backend fully supported it.
+  - The library browser dropped the `授权` tab entirely — `GET/PUT/DELETE
+    .../grants` and `PUT .../independent-permission` had no caller. Permission
+    editing is the point of the back office, and it was unreachable.
+
+  Diffing the route table against the frontend's `api()` call sites catches this;
+  reading the new page does not.
+
+## Deferred
+
+- `/admin` (admin-web) stays a separate project. It has its own design language
+  (`saas-*` classes, `surface-*`/`primary-*` scales) and a different audience;
+  merging it is not motivated by shared code.
+- The `search` and `settings` tabs remain placeholders, as they were server-side.
+- Serving `/admin` and `/database` from a single SPA, which would remove the
+  `appDir` collision constraint entirely.