refactor(axios): split lib/axios.ts into factory + default + portal-token instances

The single axios.ts file becomes a directory with:
- factory.ts — createApiClient + the registerDefaultInterceptors /
  registerPortalTokenInterceptors seam (preserves the
  TECH-AXIOS-STORE-COUPLING decoupling — no store imports inside)
- default.ts — cookie-authenticated client (organizer + cookie-auth
  portal flows; existing 45 call sites resolve unchanged)
- portal-token.ts — Bearer-auth client for the artist-advance /
  supplier-intake flows (forward-compatible groundwork; no active
  consumers today)
- index.ts — re-exports apiClient + portalApiClient + the register* /
  createApiClient surface; the existing `import { apiClient } from
  '@/lib/axios'` continues to work directory-resolved.

The bindings plugin (plugins/3.axios-bindings.ts) now wires both
clients with a shared deps base + flavour-specific overrides. The
`getPortalToken` callback returns null until Phase E surfaces
`portalToken` on useAuthStore — no current consumers exercise the
Bearer path, so the null-return is intentional placeholder.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/app/src/plugins/3.axios-bindings.ts

@@ -1,5 +1,10 @@
 import type { App } from 'vue'
-import { apiClient, registerInterceptors } from '@/lib/axios'
+import {
+  apiClient,
+  portalApiClient,
+  registerDefaultInterceptors,
+  registerPortalTokenInterceptors,
+} from '@/lib/axios'
 import { useAuthStore } from '@/stores/useAuthStore'
 import { useImpersonationStore } from '@/stores/useImpersonationStore'
 import { useNotificationStore } from '@/stores/useNotificationStore'
@@ -10,10 +15,9 @@ import { useOrganisationStore } from '@/stores/useOrganisationStore'
 // inside each callback (not eagerly at plugin-init), which keeps the
 // seam tolerant of any future plugin-ordering changes.
 export default function (_: App): void {
-  registerInterceptors(apiClient, {
-    getActiveOrgId: () => useOrganisationStore().activeOrganisationId,
-    getImpersonationTargetUserId: () => useImpersonationStore().targetUserId,
-    notify: (message, level) => useNotificationStore().show(message, level),
+  const sharedDeps = {
+    notify: (message: string, level: 'error' | 'warning') =>
+      useNotificationStore().show(message, level),
     onAuthFail: () => {
       const authStore = useAuthStore()
       if (authStore.isInitialized)
@@ -23,5 +27,21 @@ export default function (_: App): void {
       useImpersonationStore().clearState()
       window.location.href = '/platform'
     },
+  }
+
+  registerDefaultInterceptors(apiClient, {
+    ...sharedDeps,
+    getActiveOrgId: () => useOrganisationStore().activeOrganisationId,
+    getImpersonationTargetUserId: () => useImpersonationStore().targetUserId,
+  })
+
+  registerPortalTokenInterceptors(portalApiClient, {
+    ...sharedDeps,
+
+    getPortalToken: () => {
+      const authStore = useAuthStore() as unknown as { portalToken?: string | null }
+
+      return authStore.portalToken ?? null
+    },
   })
 }