Change ResourceCache to use OrderedDict for performance

[brian-hussey]

🐛 Bug-fix PR

Before opening this PR please:

1. make lint - passes ruff, mypy, pylint
2. make test - all unit + integration tests green
3. make coverage - ≥ 90 %
4. make docker docker-run-ssl or make podman podman-run-ssl
5. Update relevant documentation.
6. Tested with sqlite and postgres + redis.
7. Manual regression no longer fails. Ensure the UI and /version work correctly.

---

📌 Summary

This change addresses #1614. It works in the suggested change, ensures tests work as expected and make the tests more robust for the new model.
It removes the need for the "last_accessed" property in the CacheEntry class/objects.

🔁 Reproduction Steps

Link the issue and minimal steps to reproduce the bug.

🐞 Root Cause

Implementation of the cache could be improved.

💡 Fix Description

Using the suggested OrderedDict approach and testing around that.

🧪 Verification

Check	Command	Status
Lint suite	make lint
Unit tests	make test
Coverage ≥ 90 %	make coverage
Manual regression no longer fails	steps / screenshots

📐 MCP Compliance (if relevant)

• Matches current MCP spec
• No breaking change to MCP clients

✅ Checklist

• Code formatted (make black isort pre-commit)
• No secrets/credentials committed

[crivetimihai]

Closes #1614

[crivetimihai]

@brian-hussey Rebased and tested. The PR correctly implements the optimization described in issue #1614:

Aspect	Original	New (PR)
Storage	Dict[str, CacheEntry]	OrderedDict[str, CacheEntry]
LRU Tracking	last_access field in CacheEntry	OrderedDict maintains order
Eviction	O(n) min() scan	O(1) popitem(last=False)
Access Update	entry.last_access = now	move_to_end(key)

Bonus fix: The old code had a bug where updating an existing key at full capacity would unnecessarily evict another entry. The new code
handles this correctly.

Performance Benchmark Results

Cache Size	Eviction Speedup	Mixed Workload Speedup
100	8.5x	4.7x
500	35.5x	18.5x
1000	70.5x	38x
5000	305x	-

The improvement scales linearly with cache size (O(n) → O(1)).

Please re-test after merge.