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/timeout.go

@@ -0,0 +1,48 @@
+package middleware
+
+import (
+	"context"
+	"net/http"
+	"time"
+)
+
+// Timeout is a middleware that cancels ctx after a given timeout and return
+// a 504 Gateway Timeout error to the client.
+//
+// It's required that you select the ctx.Done() channel to check for the signal
+// if the context has reached its deadline and return, otherwise the timeout
+// signal will be just ignored.
+//
+// ie. a route/handler may look like:
+//
+//	r.Get("/long", func(w http.ResponseWriter, r *http.Request) {
+//		ctx := r.Context()
+//		processTime := time.Duration(rand.Intn(4)+1) * time.Second
+//
+//		select {
+//		case <-ctx.Done():
+//			return
+//
+//		case <-time.After(processTime):
+//			// The above channel simulates some hard work.
+//		}
+//
+//		w.Write([]byte("done"))
+//	})
+func Timeout(timeout time.Duration) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			ctx, cancel := context.WithTimeout(r.Context(), timeout)
+			defer func() {
+				cancel()
+				if ctx.Err() == context.DeadlineExceeded {
+					w.WriteHeader(http.StatusGatewayTimeout)
+				}
+			}()
+
+			r = r.WithContext(ctx)
+			next.ServeHTTP(w, r)
+		}
+		return http.HandlerFunc(fn)
+	}
+}