docs: Add comprehensive component architecture documentation

Created detailed architectural documentation showing component interactions,
communication patterns, and data flows across all StellaOps services.

## New Documentation

**docs/ARCHITECTURE_DETAILED.md** - Comprehensive architecture guide:
- Component topology diagram (all 36+ services)
- Infrastructure layer details (PostgreSQL, Valkey, RustFS, NATS)
- Service-by-service catalog with responsibilities
- Communication patterns with WHY (business purpose)
- 5 detailed data flow diagrams:
  1. Scan Request Flow (CLI → Scanner → Worker → Policy → Signer → Attestor → Notify)
  2. Advisory Update Flow (Concelier → Scheduler → Scanner re-evaluation)
  3. VEX Update Flow (Excititor → IssuerDirectory → Scheduler → Policy)
  4. Notification Delivery Flow (Scanner → Valkey → Notify → Slack/Teams/Email)
  5. Policy Evaluation Flow (Scanner → Policy.Gateway → OPA → PostgreSQL replication)
- Database schema isolation details per service
- Security boundaries and authentication flows

## Updated Documentation

**docs/DEVELOPER_ONBOARDING.md**:
- Added link to detailed architecture
- Simplified overview with component categories
- Quick reference topology tree

**docs/07_HIGH_LEVEL_ARCHITECTURE.md**:
- Updated infrastructure requirements section
- Clarified PostgreSQL as ONLY database
- Emphasized Valkey as REQUIRED (not optional)
- Marked NATS as optional (Valkey is default transport)

**docs/README.md**:
- Added link to detailed architecture in navigation

## Key Architectural Insights Documented

**Communication Patterns:**
- 11 communication steps in scan flow (Gateway → Scanner → Valkey → Worker → Concelier → Policy → Signer → Attestor → Valkey → Notify → Slack)
- PostgreSQL logical replication (advisory_raw_stream, vex_raw_stream → Policy Engine)
- Valkey Streams for async job queuing (XADD/XREADGROUP pattern)
- HTTP webhooks for delta events (Concelier/Excititor → Scheduler)

**Security Boundaries:**
- Authority issues OpToks with DPoP binding (RFC 9449)
- Signer enforces PoE validation + scanner digest verification
- All services validate JWT + DPoP on every request
- Tenant isolation via tenant_id in all PostgreSQL queries

**Database Patterns:**
- 8 dedicated PostgreSQL schemas (authority, scanner, vuln, vex, scheduler, notify, policy, orchestrator)
- Append-only advisory/VEX storage (AOC - Aggregation-Only Contract)
- BOM-Index for impact selection (CVE → PURL → image mapping)

This documentation provides complete visibility into who calls who, why they
communicate, what data flows through the system, and how security is enforced
at every layer.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/DEVELOPER_ONBOARDING.md

@@ -19,7 +19,62 @@
 
 StellaOps is a deterministic SBOM + VEX platform built as a microservices architecture with 36+ services organized into functional domains.
 
-### Runtime Topology - High-Level
+**📖 For detailed component architecture with communication patterns, see [ARCHITECTURE_DETAILED.md](./ARCHITECTURE_DETAILED.md)**
+
+### Quick Reference - Component Topology
+
+```
+CLIENT LAYER
+├─ stella CLI                    → Gateway (JWT + DPoP auth)
+├─ Web UI (Angular)              → Gateway (JWT + DPoP auth)
+├─ CI/CD Pipelines               → Gateway (JWT + DPoP auth)
+└─ Zastava Observer              → Scanner (runtime scans)
+
+INFRASTRUCTURE (REQUIRED)
+├─ PostgreSQL v16+               → Primary database (ALL services)
+├─ Valkey v8.0                   → Cache, DPoP, queues, events
+└─ RustFS                        → Object storage (S3 API)
+
+INFRASTRUCTURE (OPTIONAL)
+└─ NATS JetStream                → Alternative messaging (Valkey is default)
+
+GATEWAY LAYER
+└─ Gateway.WebService            → Auth, routing, rate limiting
+
+AUTH & CRYPTO
+├─ Authority                     → OAuth2/OIDC, OpTok issuance
+├─ Signer                        → DSSE signing (FIPS/GOST/SM)
+└─ Attestor                      → Rekor v2 transparency log
+
+CORE ENGINES
+├─ Scanner.WebService            → Scan orchestration
+├─ Scanner.Worker                → Image analysis, SBOM generation
+├─ Concelier.WebService          → Advisory ingestion (NVD, Red Hat, etc.)
+├─ Excititor.WebService          → VEX ingestion + consensus
+├─ Policy.Gateway                → OPA/Rego policy evaluation
+├─ Scheduler.WebService          → Re-scan orchestration
+├─ Notify.WebService             → Notification orchestration
+├─ Notify.Worker                 → Slack/Teams/Email delivery
+└─ Orchestrator.WebService       → DAG workflows, pack runs
+
+SUPPORTING
+└─ IssuerDirectory               → VEX issuer trust registry
+```
+
+### Service Categories
+
+| Category | Services | Purpose |
+|----------|----------|---------|
+| **Gateway** | Gateway.WebService | API routing, auth enforcement |
+| **Auth & Security** | Authority, Signer, Attestor | OAuth2, signing, transparency |
+| **Scanning** | Scanner.Web, Scanner.Worker | Container analysis, SBOM |
+| **Advisory** | Concelier.Web, Concelier.Worker | Vulnerability ingestion |
+| **VEX** | Excititor.Web, Excititor.Worker | Exploitability statements |
+| **Policy** | Policy.Gateway, Policy Engine | OPA/Rego evaluation |
+| **Orchestration** | Scheduler, Orchestrator | Job coordination |
+| **Notifications** | Notify.Web, Notify.Worker | Delivery to Slack/Teams/Email |
+
+### Runtime Topology - Infrastructure Dependencies
 
 ```
 ┌─────────────────────────────────────────────────────────────────────┐