Set Valkey memory and eviction defaults

[pshankinclarke]

✍️ Description

This responds to "Enable memory-optimized settings for small-scale deployments" in discussion #3446.

I reserve 25% of container's RAM and use 75% for Valkey (see ElastiCache memory management) by setting maxmemory in valkey.conf (see memory allocation).

I also set cache defaults tuned for small deployments (see https://valkey.io/topics/lru-cache/):

• maxmemory-policy allkeys-lru
• maxmemory samples 10

🔗 Related PR / Issue

Link: #
discussion #3446

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.