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/basic_auth.go

@@ -0,0 +1,33 @@
+package middleware
+
+import (
+	"crypto/subtle"
+	"fmt"
+	"net/http"
+)
+
+// BasicAuth implements a simple middleware handler for adding basic http auth to a route.
+func BasicAuth(realm string, creds map[string]string) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			user, pass, ok := r.BasicAuth()
+			if !ok {
+				basicAuthFailed(w, realm)
+				return
+			}
+
+			credPass, credUserOk := creds[user]
+			if !credUserOk || subtle.ConstantTimeCompare([]byte(pass), []byte(credPass)) != 1 {
+				basicAuthFailed(w, realm)
+				return
+			}
+
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
+func basicAuthFailed(w http.ResponseWriter, realm string) {
+	w.Header().Add("WWW-Authenticate", fmt.Sprintf(`Basic realm="%s"`, realm))
+	w.WriteHeader(http.StatusUnauthorized)
+}