feat: add index-applier container for deferred index creation
Implements automated index application for the APPLYING_INDEXES sync state. The index-applier container polls the API until the sync stage transitions to APPLYING_INDEXES, then applies all indexes from db-indexes.yaml using CREATE INDEX CONCURRENTLY. Changes: - Add apply-indexes.sh script with idempotent logic and invalid index handling - Add curl, jq, yq dependencies to postgres Dockerfile - Add docker-compose-index-applier.yaml service definition - Include index-applier in main docker-compose.yaml - Add index-management.md documentation in advanced-configuration - Update docker.md deployment guide with index application section The script: - Polls /network/status for APPLYING_INDEXES stage - Detects and drops invalid indexes (from failed CONCURRENTLY operations) - Creates indexes sequentially using CONCURRENTLY to avoid indexer restarts - Reads index definitions from db-indexes.yaml (single source of truth)