feat(gallery): add public templates gallery frontend (Tasks 4 & 5)

Add types, API client, page component, card components, detail modal,
and /templates route for the public templates gallery. Uses raw fetch()
for unauthenticated access, glass-card design system, and URL-synced
filters with debounced search.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/api/index.ts

@@ -28,3 +28,4 @@ export { aiSessionsApi } from './aiSessions'
 export { flowProposalsApi } from './flowProposals'
 export { flowpilotAnalyticsApi } from './flowpilotAnalytics'
 export { notificationsApi } from './notifications'
+export { publicTemplatesApi } from './publicTemplates'

frontend/src/api/publicTemplates.ts

@@ -0,0 +1,54 @@
+import type {
+  PublicGalleryResponse,
+  PublicFlowDetail,
+  PublicScriptDetail,
+  GalleryCategory,
+} from '@/types/public-templates'
+
+const API_URL = import.meta.env.VITE_API_URL || 'http://localhost:8000'
+
+export const publicTemplatesApi = {
+  async listGallery(params?: {
+    category?: string
+    type?: string
+    sort?: string
+    page?: number
+    per_page?: number
+  }): Promise<PublicGalleryResponse> {
+    const searchParams = new URLSearchParams()
+    if (params?.category) searchParams.set('category', params.category)
+    if (params?.type) searchParams.set('type', params.type)
+    if (params?.sort) searchParams.set('sort', params.sort)
+    if (params?.page) searchParams.set('page', String(params.page))
+    if (params?.per_page) searchParams.set('per_page', String(params.per_page))
+    const qs = searchParams.toString()
+    const response = await fetch(`${API_URL}/api/v1/public/templates${qs ? `?${qs}` : ''}`)
+    if (!response.ok) throw new Error('Failed to load gallery')
+    return response.json()
+  },
+
+  async getFlowDetail(id: string): Promise<PublicFlowDetail> {
+    const response = await fetch(`${API_URL}/api/v1/public/templates/flows/${id}`)
+    if (!response.ok) throw new Error('Failed to load flow detail')
+    return response.json()
+  },
+
+  async getScriptDetail(id: string): Promise<PublicScriptDetail> {
+    const response = await fetch(`${API_URL}/api/v1/public/templates/scripts/${id}`)
+    if (!response.ok) throw new Error('Failed to load script detail')
+    return response.json()
+  },
+
+  async listCategories(): Promise<GalleryCategory[]> {
+    const response = await fetch(`${API_URL}/api/v1/public/templates/categories`)
+    if (!response.ok) throw new Error('Failed to load categories')
+    return response.json()
+  },
+
+  async search(q: string): Promise<PublicGalleryResponse> {
+    const searchParams = new URLSearchParams({ q })
+    const response = await fetch(`${API_URL}/api/v1/public/templates/search?${searchParams}`)
+    if (!response.ok) throw new Error('Search failed')
+    return response.json()
+  },
+}