feat(server): org-scope service layer + handlers + org admin API

Threads org_id through every admin-facing service function (servers, keys,
assignments, secrets, workflows/steps/runs, monitors, channels, audit),
adds RequireRole middleware, and wires /api/org user + OIDC management
routes. Agent/scheduler paths keep unique-key signatures and resolve org
from the loaded record; internal-only helpers (getServerByID,
getRunByID, getMonitorByID) preserve those call sites.

server/internal/auth/middleware.go

@@ -35,6 +35,19 @@ func UserID(c *gin.Context) string {
 	return ""
 }
 
+func RequireRole(roles ...string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		r := Role(c)
+		for _, want := range roles {
+			if r == want {
+				c.Next()
+				return
+			}
+		}
+		c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"error": "insufficient role"})
+	}
+}
+
 func Middleware() gin.HandlerFunc {
 	return func(c *gin.Context) {
 		cookie, err := c.Request.Cookie(sessionCookieName)