fix(infra): resolve fresh-build DB schema gaps, Kerberos warnings, and Dockerfile syntax

- Workflow: add PostgreSQL auto-migration (8 tables in schema `workflow`)
  with AddStartupMigrations wiring and embedded SQL migration
- Scheduler: add missing `schema_version` and `source` columns to
  `scheduler.schedules` table in both init script and migration
- Platform: delay analytics maintenance 15s to avoid race with migration
  020_AnalyticsRollups creating compute_daily_rollups()
- Docker: install libgssapi-krb5-2 in runtime image to eliminate Npgsql
  Kerberos probe warnings across all 59 services
- Docker: remove `# syntax=docker/dockerfile:1.7` directive from both
  Dockerfiles to avoid BuildKit frontend pull failures on flaky DNS
- Postgres init: add `workflow` schema to 01-create-schemas.sql

Verified: 75 containers, 0 unhealthy, 0 recurring errors after full
wipe-and-rebuild cycle.

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

devops/compose/postgres-init/01-create-schemas.sql

@@ -15,3 +15,4 @@ CREATE SCHEMA IF NOT EXISTS issuer_directory;
 CREATE SCHEMA IF NOT EXISTS analytics;
 CREATE SCHEMA IF NOT EXISTS scheduler_app;
 CREATE SCHEMA IF NOT EXISTS findings_ledger_app;
+CREATE SCHEMA IF NOT EXISTS workflow;