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>

vendor/github.com/golang-migrate/migrate/v4/database/error.go

@@ -0,0 +1,27 @@
+package database
+
+import (
+	"fmt"
+)
+
+// Error should be used for errors involving queries ran against the database
+type Error struct {
+	// Optional: the line number
+	Line uint
+
+	// Query is a query excerpt
+	Query []byte
+
+	// Err is a useful/helping error message for humans
+	Err string
+
+	// OrigErr is the underlying error
+	OrigErr error
+}
+
+func (e Error) Error() string {
+	if len(e.Err) == 0 {
+		return fmt.Sprintf("%v in line %v: %s", e.OrigErr, e.Line, e.Query)
+	}
+	return fmt.Sprintf("%v in line %v: %s (details: %v)", e.Err, e.Line, e.Query, e.OrigErr)
+}