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/go-chi/chi/v5/middleware/get_head.go

@@ -0,0 +1,39 @@
+package middleware
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// GetHead automatically route undefined HEAD requests to GET handlers.
+func GetHead(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == "HEAD" {
+			rctx := chi.RouteContext(r.Context())
+			routePath := rctx.RoutePath
+			if routePath == "" {
+				if r.URL.RawPath != "" {
+					routePath = r.URL.RawPath
+				} else {
+					routePath = r.URL.Path
+				}
+			}
+
+			// Temporary routing context to look-ahead before routing the request
+			tctx := chi.NewRouteContext()
+
+			// Attempt to find a HEAD handler for the routing path, if not found, traverse
+			// the router as through its a GET route, but proceed with the request
+			// with the HEAD method.
+			if !rctx.Routes.Match(tctx, "HEAD", routePath) {
+				rctx.RouteMethod = "GET"
+				rctx.RoutePath = routePath
+				next.ServeHTTP(w, r)
+				return
+			}
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}