feat: org capacity policy admin surface

ADR-0022 / Spec.System.Capacity pins layered capacity limits: a platform
ceiling per dimension is unbreakable, and each organization may only set a
lower `organizationLimit`. The effective limit is the minimum of the two
(`LayeredLimit.effective`); dimensions with no org override fall back to
the platform ceiling. No dimension may be unlimited (a ceiling must exist
before an org limit can be set, `LayeredLimit.Valid`).

Add the backend: the pinned 23 CapacityDimension set + labels
(src/capacity/dimensions.ts), platform ceilings sourced from existing
runtime env vars plus `HUB_CEILING_<DIMENSION>` (src/capacity/ceilings.ts),
the OrganizationCapacityPolicy prisma model + migration, the
getCapacityPolicy/setCapacityPolicy service enforcing LayeredLimit.Valid,
and org-admin GET/PUT /api/org/:orgSlug/capacity-policy routes wired into
the org route tree.

Add the admin-web surface: CapacityDimension/CapacityPolicyView api client
types, capacityPolicy/setCapacityPolicy methods, a `容量` nav entry, and a
capacity page that lists every dimension with its platform ceiling (or
`未配置` when unset), an org-limit input (disabled until a ceiling exists),
and a live effective-value column. Saving sends the partial limits map;
the service rejects values above the ceiling or for unconfigured dimensions.

hub/src/admin/routes/orgRoutes.ts

@@ -15,6 +15,7 @@ import { registerMembersRoutes } from "./membersRoutes.js";
 import { registerSessionsAndUsageRoutes } from "./sessionsRoutes.js";
 import { registerTeamsRoutes } from "./teamsRoutes.js";
 import { registerProviderConnectionRoutes } from "./providerConnectionRoutes.js";
+import { registerCapacityRoutes } from "./capacityRoutes.js";
 import type { LocalSecretEnvelope } from "../../security/secretEnvelope.js";
 import type { ProviderReadinessProbe } from "../../connections/providerReadiness.js";
 import type { FeishuReadinessProbe } from "../../connections/feishuReadiness.js";
@@ -105,6 +106,10 @@ export async function registerOrgRoutes(app: FastifyInstance, config: OrgRouteCo
     prisma: config.prisma,
     sessionSecret: config.sessionSecret,
   });
+  await registerCapacityRoutes(app, {
+    prisma: config.prisma,
+    sessionSecret: config.sessionSecret,
+  });
   await registerSessionsAndUsageRoutes(app, {
     prisma: config.prisma,
     sessionSecret: config.sessionSecret,