ci: use lambdaclass/actions reusable workflows for AI review (#69)

## Summary
- Consolidate three separate AI review workflows into a unified workflow
using reusable workflows from lambdaclass/actions
- Rename prompt file to match standardized naming convention
- Enable on-demand reviews via `/kimi`, `/codex`, `/claude` commands

## Changes
- Add `.github/workflows/ai-review.yml` - unified workflow using
lambdaclass/actions@v1
- Rename `.github/prompts/pr_review.md` → `ai-review.md`
- Remove legacy workflows: `pr_review_chatgpt.yaml`,
`pr_review_claude.yaml`, `pr_review_kimi.yaml`

## Test plan
- [ ] Verify workflow runs on PR open/ready_for_review
- [ ] Test on-demand review commands (`/kimi`, `/codex`, `/claude`)
- [ ] Confirm all three AI reviewers execute in parallel
- [ ] Validate custom prompt is read from new location

Author: MegaRedHand

.github/prompts/pr_review.md .github/prompts/ai-review.md.github/prompts/pr_review.md renamed to .github/prompts/ai-review.md

@@ -0,0 +1,36 @@
+# AI Code Review using lambdaclass/actions reusable workflows
+#
+# Triggers:
+# - Automatically on PR open/ready_for_review
+# - On-demand via PR comments: /kimi, /codex, /claude (requires write access)
+#
+# Custom prompt: .github/prompts/ai-review.md
+#
+# Required secrets:
+# - KIMI_API_KEY: For Kimi reviews (https://platform.moonshot.ai/)
+# - OPENAI_API_KEY: For Codex reviews (https://platform.openai.com/)
+# - ANTHROPIC_API_KEY: For Claude reviews (https://console.anthropic.com/)
+
+name: AI Code Review
+
+on:
+  pull_request:
+    types: [opened, ready_for_review]
+  issue_comment:
+    types: [created]
+
+jobs:
+  kimi-review:
+    uses: lambdaclass/actions/.github/workflows/ai-review-kimi.yml@v1
+    secrets:
+      KIMI_API_KEY: ${{ secrets.KIMI_API_KEY }}
+
+  codex-review:
+    uses: lambdaclass/actions/.github/workflows/ai-review-codex.yml@v1
+    secrets:
+      OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
+
+  claude-review:
+    uses: lambdaclass/actions/.github/workflows/ai-review-claude.yml@v1
+    secrets:
+      ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}