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/util.go

@@ -0,0 +1,33 @@
+package database
+
+import (
+	"fmt"
+	"go.uber.org/atomic"
+	"hash/crc32"
+	"strings"
+)
+
+const advisoryLockIDSalt uint = 1486364155
+
+// GenerateAdvisoryLockId inspired by rails migrations, see https://goo.gl/8o9bCT
+func GenerateAdvisoryLockId(databaseName string, additionalNames ...string) (string, error) { // nolint: golint
+	if len(additionalNames) > 0 {
+		databaseName = strings.Join(append(additionalNames, databaseName), "\x00")
+	}
+	sum := crc32.ChecksumIEEE([]byte(databaseName))
+	sum = sum * uint32(advisoryLockIDSalt)
+	return fmt.Sprint(sum), nil
+}
+
+// CasRestoreOnErr CAS wrapper to automatically restore the lock state on error
+func CasRestoreOnErr(lock *atomic.Bool, o, n bool, casErr error, f func() error) error {
+	if !lock.CAS(o, n) {
+		return casErr
+	}
+	if err := f(); err != nil {
+		// Automatically unlock/lock on error
+		lock.Store(o)
+		return err
+	}
+	return nil
+}