perf(ci): reduce build memory and CPU allocations

Scale down memory limits and parallelization settings across CI build pipeline. Reduce heap from 8g to 4g, metaspace from 1g to 512m, worker count from 4 to 2, and CMAKE build parallel level from 8 to 4. Remove Gradle caching and update web export to use explicit NODE_OPTIONS for memory allocation. These optimizations reduce resource usage while maintaining stable builds.

plugins/withCmakeJobLimit.js

@@ -2,7 +2,7 @@ const { withDangerousMod } = require('@expo/config-plugins');
 const fs = require('fs');
 const path = require('path');
 
-const MAX_JOBS = '8';
+const MAX_JOBS = '4';
 
 // React Native's hermes-engine build hardcodes
 //   Runtime.getRuntime().availableProcessors()