feat(docker-watcher): phase 12 - hardening

Blue-green zero-downtime deploys, promote flow validation.
Dual auth: local (bcrypt + JWT) and OAuth2/OIDC (any provider).
Auth middleware, login page, auth settings UI.
Structured logging (slog JSON), config export to YAML.
Graceful shutdown with deploy draining.
Multi-stage Dockerfile and production docker-compose.yml.
Swap phase order: Volumes & Env before UI Polish.

internal/auth/middleware.go

@@ -0,0 +1,68 @@
+package auth
+
+import (
+	"context"
+	"net/http"
+	"strings"
+)
+
+// contextKey is the type for context value keys used by the auth package.
+type contextKey string
+
+const claimsKey contextKey = "auth_claims"
+
+// Middleware returns an HTTP middleware that protects routes by requiring a valid JWT.
+// It extracts the token from the Authorization header (Bearer scheme) or the "token"
+// query parameter (for SSE connections).
+// Unauthenticated requests receive a 401 JSON response.
+func Middleware(la *LocalAuth) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			tokenStr := extractToken(r)
+			if tokenStr == "" {
+				http.Error(w, `{"success":false,"error":"authentication required"}`, http.StatusUnauthorized)
+				return
+			}
+
+			claims, err := la.ValidateToken(tokenStr)
+			if err != nil {
+				http.Error(w, `{"success":false,"error":"invalid or expired token"}`, http.StatusUnauthorized)
+				return
+			}
+
+			ctx := context.WithValue(r.Context(), claimsKey, claims)
+			next.ServeHTTP(w, r.WithContext(ctx))
+		})
+	}
+}
+
+// AdminOnly returns an HTTP middleware that requires the authenticated user to have
+// the "admin" role.
+func AdminOnly(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		claims, ok := ClaimsFromContext(r.Context())
+		if !ok || claims.Role != "admin" {
+			http.Error(w, `{"success":false,"error":"admin access required"}`, http.StatusForbidden)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+// ClaimsFromContext retrieves the authenticated user's claims from the request context.
+func ClaimsFromContext(ctx context.Context) (Claims, bool) {
+	claims, ok := ctx.Value(claimsKey).(Claims)
+	return claims, ok
+}
+
+// extractToken gets the JWT from the Authorization header or "token" query param.
+func extractToken(r *http.Request) string {
+	// Try Authorization: Bearer <token>
+	authHeader := r.Header.Get("Authorization")
+	if strings.HasPrefix(authHeader, "Bearer ") {
+		return strings.TrimPrefix(authHeader, "Bearer ")
+	}
+
+	// Fall back to query parameter (used by SSE and browser-based connections).
+	return r.URL.Query().Get("token")
+}