[AZ-486] F7 endpoint builders + STC-ARCH-02 (cycle 1 close)

Single source of truth for every /api/<service>/... URL the UI talks to:
src/api/endpoints.ts (25 typed builders) re-exported via the F4 barrel.
Migrates 13 production callsites in admin / annotations / flights /
settings / dataset / auth / api-client / FlightContext / DetectionClasses
to endpoints.* . Adds the STC-ARCH-02 static gate (--mode=api-literals
in scripts/check-arch-imports.mjs, wired into scripts/run-tests.sh)
that fails any new hardcoded /api/<service>/ literal in src/ outside
endpoints.ts and *.test.tsx? files.

Tests: +36 contract assertions in src/api/endpoints.test.ts (every
builder, character-identical), +6 STC-ARCH-02 architecture cases in
tests/architecture_imports.test.ts (single / double / template literal
fail paths, *.test.* exemption, line-comment skip, migrated codebase
pass). Fast profile 167 -> 209 PASS / 13 SKIP / 0 FAIL, +42 new,
0 regressions. Static profile 31 / 31 PASS.

Closes architecture baseline finding F7. Cycle 1 of Phase B closed.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/features/dataset/DatasetPage.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback } from 'react'
 import { useTranslation } from 'react-i18next'
-import { api } from '../../api'
+import { api, endpoints } from '../../api'
 import { useDebounce, useResizablePanel } from '../../hooks'
 import { useFlight, DetectionClasses, ConfirmDialog } from '../../components'
 import CanvasEditor from '../annotations/CanvasEditor'
@@ -42,7 +42,7 @@ export default function DatasetPage() {
     if (objectsOnly) params.set('hasDetections', 'true')
     if (debouncedSearch) params.set('name', debouncedSearch)
     try {
-      const res = await api.get<PaginatedResponse<DatasetItem>>(`/api/annotations/dataset?${params}`)
+      const res = await api.get<PaginatedResponse<DatasetItem>>(endpoints.annotations.dataset(params.toString()))
       setItems(res.items)
       setTotalCount(res.totalCount)
     } catch {}
@@ -52,7 +52,7 @@ export default function DatasetPage() {
 
   const handleDoubleClick = async (item: DatasetItem) => {
     try {
-      const ann = await api.get<AnnotationListItem>(`/api/annotations/dataset/${item.annotationId}`)
+      const ann = await api.get<AnnotationListItem>(endpoints.annotations.datasetItem(item.annotationId))
       setEditorAnnotation(ann)
       setEditorDetections(ann.detections)
       setTab('editor')
@@ -61,7 +61,7 @@ export default function DatasetPage() {
 
   const handleValidate = async () => {
     if (selectedIds.size === 0) return
-    await api.post('/api/annotations/dataset/bulk-status', {
+    await api.post(endpoints.annotations.datasetBulkStatus(), {
       annotationIds: Array.from(selectedIds),
       status: AnnotationStatus.Validated,
     })
@@ -71,7 +71,7 @@ export default function DatasetPage() {
 
   const loadDistribution = useCallback(async () => {
     try {
-      const data = await api.get<ClassDistributionItem[]>('/api/annotations/dataset/class-distribution')
+      const data = await api.get<ClassDistributionItem[]>(endpoints.annotations.datasetClassDistribution())
       setDistribution(data)
     } catch {}
   }, [])
@@ -180,7 +180,7 @@ export default function DatasetPage() {
                   } ${item.isSeed ? 'ring-2 ring-az-red' : ''}`}
                 >
                   <img
-                    src={`/api/annotations/annotations/${item.annotationId}/thumbnail`}
+                    src={endpoints.annotations.annotationThumbnail(item.annotationId)}
                     alt={item.imageName}
                     className="w-full h-32 object-cover bg-az-bg"
                     loading="lazy"