feat(enterprise-site): add PbootCMS enterprise site publisher

Introduce a new enterprise-site publishing channel that lets tenants push
articles to self-hosted PbootCMS sites alongside the existing media supply
flow.

Backend (server/internal/tenant):
- enterprise_site_service: CRUD, ping, category sync, and article publish
- enterprise_site_pbootcms: PbootCMS API client integration
- enterprise_site_crypto: encrypt/decrypt stored site credentials
- enterprise_site_handler + routes under /enterprise-sites
- migrations for the enterprise site publisher tables
- config: add SERVER_PUBLIC_BASE_URL (Server.PublicBaseURL) for callbacks
- article/media services adjusted to support the publish flow

Frontend (apps/admin-web):
- PublishArticleModal & ArticlePublishStatus: enterprise-site publish UI
- MediaView: manage enterprise sites and categories
- api + shared-types: enterprise site endpoints and types
- http-client: add PATCH method support

Integrations:
- pbootcms GeoPublisher controller plugin + install guide
- docs/enterprise-site-publisher-v1.md design doc

server/internal/shared/config/config.go

@@ -47,6 +47,7 @@ type Config struct {
 type ServerConfig struct {
 	Port            int             `mapstructure:"port"`
 	Mode            string          `mapstructure:"mode"`
+	PublicBaseURL   string          `mapstructure:"public_base_url"`
 	TrustedProxies  []string        `mapstructure:"trusted_proxies"`
 	AllowedOrigins  []string        `mapstructure:"allowed_origins"`
 	SecurityHeaders SecurityHeaders `mapstructure:"security_headers"`
@@ -1193,6 +1194,9 @@ func applyEnvOverrides(cfg *Config) {
 	if origins, ok := lookupNonEmptyEnv("SERVER_ALLOWED_ORIGINS"); ok {
 		cfg.Server.AllowedOrigins = strings.Split(origins, ",")
 	}
+	if publicBaseURL, ok := lookupNonEmptyEnv("SERVER_PUBLIC_BASE_URL"); ok {
+		cfg.Server.PublicBaseURL = publicBaseURL
+	}
 	if enabled, ok := lookupBoolEnv("SERVER_SECURITY_HEADERS_ENABLED"); ok {
 		cfg.Server.SecurityHeaders.Enabled = enabled
 	}