feat: add CAMELEER_CORS_ALLOWED_ORIGINS for multi-origin CORS support

Behind a reverse proxy the browser sends Origin matching the proxy's
public URL, which the single-origin CAMELEER_UI_ORIGIN rejects.
New env var accepts comma-separated origins and takes priority over
UI_ORIGIN, which remains as a backwards-compatible fallback.

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

CLAUDE.md

@@ -41,7 +41,7 @@ java -jar cameleer3-server-app/target/cameleer3-server-app-1.0-SNAPSHOT.jar
 - Multi-tenancy: each server instance serves one tenant (configured via `CAMELEER_TENANT_ID`, default: `"default"`). Environments (dev/staging/prod) are first-class — agents send `environmentId` at registration and in heartbeats. JWT carries `env` claim for environment persistence across token refresh. PostgreSQL isolated via schema-per-tenant (`?currentSchema=tenant_{id}`). ClickHouse shared DB with `tenant_id` + `environment` columns, partitioned by `(tenant_id, toYYYYMM(timestamp))`.
 - Storage: PostgreSQL for RBAC, config, and audit; ClickHouse for all observability data (executions, search, logs, metrics, stats, diagrams). ClickHouse schema migrations in `clickhouse/*.sql`, run idempotently on startup by `ClickHouseSchemaInitializer`. Use `IF NOT EXISTS` for CREATE and ADD PROJECTION.
 - Logging: ClickHouse JDBC set to INFO (`com.clickhouse`), HTTP client to WARN (`org.apache.hc.client5`) in application.yml
-- Security: JWT auth with RBAC (AGENT/VIEWER/OPERATOR/ADMIN roles), Ed25519 config signing (key derived deterministically from JWT secret via HMAC-SHA256), bootstrap token for registration
+- Security: JWT auth with RBAC (AGENT/VIEWER/OPERATOR/ADMIN roles), Ed25519 config signing (key derived deterministically from JWT secret via HMAC-SHA256), bootstrap token for registration. CORS: `CAMELEER_CORS_ALLOWED_ORIGINS` (comma-separated) overrides `CAMELEER_UI_ORIGIN` for multi-origin setups (e.g., reverse proxy).
 - OIDC: Optional external identity provider support (token exchange pattern). Configured via admin API, stored in database (`server_config` table). Resource server mode: accepts external access tokens (Logto M2M) via JWKS validation when `CAMELEER_OIDC_ISSUER_URI` is set. `CAMELEER_OIDC_JWK_SET_URI` overrides JWKS discovery for container networking. `CAMELEER_OIDC_TLS_SKIP_VERIFY=true` disables TLS cert verification for OIDC calls (self-signed CAs). Scope-based role mapping: `admin`/`operator`/`viewer` scopes map to RBAC roles.
 - User persistence: PostgreSQL `users` table, admin CRUD at `/api/v1/admin/users`
 - Usage analytics: ClickHouse `usage_events` table tracks authenticated UI requests, flushed every 5s