docs: DevOps documentation — complete docs/devops/ set

Adds the full devops-documentation OpenSpec change implementation.
Separate from docs/developers/ — serves a different audience (operators,
not API consumers).

docs/devops/:
- README.md          — index and system overview
- architecture.md    — components, ports, data flow, Redis key patterns
- environment-variables.md — all 7 env vars (required + optional, formats, .env example)
- database.md        — 4-table schema, indexes, constraints, migration runner
- local-development.md — docker-compose setup, health checks, startup, Dockerfile gap noted
- security.md        — RSA key generation/rotation, CORS, bcrypt, secret storage guidance
- operations.md      — startup order, graceful shutdown, log reference, troubleshooting

QA gates: 48/48 tasks complete. All env vars verified against source.
All table names verified against migrations. All ports verified against
docker-compose.yml. All internal links resolve.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

openspec/changes/devops-documentation/proposal.md

@@ -0,0 +1,19 @@
+## Why
+
+SentryAgent.ai AgentIdP Phase 1 MVP is complete and `docs/developers/` covers API consumers. However, there is no documentation for the engineers who deploy, configure, and operate the infrastructure. A DevOps engineer joining the project today has no reference for environment variables, database schema, deployment procedure, security configuration, or operational runbook. We fix that now.
+
+## What Changes
+
+- New `docs/devops/` folder — fully separate from `docs/developers/` — containing a complete operational reference for DevOps engineers
+- System architecture overview: components, ports, dependencies, data flow
+- Complete environment variable reference: every variable, required vs optional, format, examples
+- Database documentation: 4-table schema, migration runner, how to apply/verify migrations
+- Local development guide: docker-compose infrastructure setup, service ports, health checks
+- Security guide: RSA keypair generation and rotation, CORS config, secret storage
+- Operations runbook: startup procedure, graceful shutdown (SIGTERM/SIGINT), logging, common failures and fixes
+
+## What Does Not Change
+
+- `docs/developers/` — not touched
+- Source code — documentation only
+- No new dependencies