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/types/index.ts

@@ -94,3 +94,4 @@ export type {
 export * from './scripts'
 export * from './integrations'
 export * from './notification'
+export type * from './public-templates'

frontend/src/types/public-templates.ts

@@ -0,0 +1,60 @@
+export interface PublicFlowTemplate {
+  id: string
+  name: string
+  description: string | null
+  category: string | null
+  tree_type: string
+  step_count: number
+  usage_count: number
+  success_rate: number | null
+  tags: string[]
+  preview_structure: Record<string, unknown> | null
+  created_at: string
+}
+
+export interface PublicScriptTemplate {
+  id: string
+  name: string
+  description: string | null
+  category_name: string | null
+  category_icon: string | null
+  complexity: string | null
+  tags: string[]
+  parameter_count: number
+  requires_elevation: boolean
+  requires_modules: string[]
+  usage_count: number
+  is_verified: boolean
+  created_at: string
+}
+
+export interface PublicGalleryResponse {
+  flow_templates: PublicFlowTemplate[]
+  script_templates: PublicScriptTemplate[]
+  total_flows: number
+  total_scripts: number
+  categories: string[]
+  domains: string[]
+}
+
+export interface PublicFlowDetail extends PublicFlowTemplate {}
+
+export interface PublicScriptDetail {
+  id: string
+  name: string
+  description: string | null
+  category_name: string | null
+  complexity: string | null
+  tags: string[]
+  parameters: Array<{ name: string; description: string; type: string }>
+  requires_elevation: boolean
+  requires_modules: string[]
+  usage_count: number
+  is_verified: boolean
+  created_at: string
+}
+
+export interface GalleryCategory {
+  name: string
+  count: number
+}