feat: Production readiness improvements for WHOOSH council formation

Major security, observability, and configuration improvements:

## Security Hardening
- Implemented configurable CORS (no more wildcards)
- Added comprehensive auth middleware for admin endpoints
- Enhanced webhook HMAC validation
- Added input validation and rate limiting
- Security headers and CSP policies

## Configuration Management
- Made N8N webhook URL configurable (WHOOSH_N8N_BASE_URL)
- Replaced all hardcoded endpoints with environment variables
- Added feature flags for LLM vs heuristic composition
- Gitea fetch hardening with EAGER_FILTER and FULL_RESCAN options

## API Completeness
- Implemented GetCouncilComposition function
- Added GET /api/v1/councils/{id} endpoint
- Council artifacts API (POST/GET /api/v1/councils/{id}/artifacts)
- /admin/health/details endpoint with component status
- Database lookup for repository URLs (no hardcoded fallbacks)

## Observability & Performance
- Added OpenTelemetry distributed tracing with goal/pulse correlation
- Performance optimization database indexes
- Comprehensive health monitoring
- Enhanced logging and error handling

## Infrastructure
- Production-ready P2P discovery (replaces mock implementation)
- Removed unused Redis configuration
- Enhanced Docker Swarm integration
- Added migration files for performance indexes

## Code Quality
- Comprehensive input validation
- Graceful error handling and failsafe fallbacks
- Backwards compatibility maintained
- Following security best practices

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

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

migrations/006_add_performance_indexes.down.sql

@@ -0,0 +1,23 @@
+-- Drop performance optimization indexes for WHOOSH
+
+-- Drop agents table performance indexes
+DROP INDEX IF EXISTS idx_agents_status_last_seen;
+
+-- Drop repositories table performance indexes
+DROP INDEX IF EXISTS idx_repositories_full_name_lookup;
+DROP INDEX IF EXISTS idx_repositories_last_issue_sync;
+
+-- Drop tasks table performance indexes
+DROP INDEX IF EXISTS idx_tasks_external_source_lookup;
+
+-- Drop council_agents table performance indexes
+DROP INDEX IF EXISTS idx_council_agents_council_lookup;
+
+-- Drop additional performance indexes
+DROP INDEX IF EXISTS idx_teams_status_task;
+DROP INDEX IF EXISTS idx_repository_webhooks_active_repo;
+DROP INDEX IF EXISTS idx_repository_sync_logs_recent;
+DROP INDEX IF EXISTS idx_task_assignments_active;
+DROP INDEX IF EXISTS idx_council_agents_deployment_status;
+DROP INDEX IF EXISTS idx_tasks_completion_analysis;
+DROP INDEX IF EXISTS idx_agents_performance_monitoring;