perf(feed): optimize moderation stage with batch author lookups (perf-optimization-agent)

- Implement `getModerationInfoForAuthors` in `ModerationService` for batching.
- Extract utility functions to `js/services/moderationUtils.js` to reduce `ModerationService` size.
- Update `createModerationStage` to use batch lookup, reducing sequential overhead.
- Benchmarks show ~50% improvement (454ms -> 227ms) for 5000 items.
- All unit tests pass.
- Task log: `docs/agents/task-logs/weekly/2026-02-22_01-25-01_perf-optimization-agent_completed.md`

Co-authored-by: PR0M3TH3AN <[email protected]>

AFTER.md

@@ -0,0 +1,23 @@
+# After Benchmark for Moderation Stage Batching
+
+## Command
+`node benchmarks/moderation_batch_bench.js`
+
+## Environment
+- Node.js v22.22.0
+- 5000 items
+- 500 authors
+- 100 muters per author
+- Forced prune check (lastPrunedAt = 0)
+
+## Results
+- Run 1: 184.34ms
+- Run 2: 277.68ms
+- Run 3: 188.89ms
+- Run 4: 256.48ms
+- **Average: ~227ms**
+
+## Comparison
+- Baseline: ~454ms
+- After: ~227ms
+- **Improvement: ~50% faster**