fix(adl): promote cached entries on hit so eviction is LRU not FIFO

[6figpsolseeker]

Summary

• The `/adl/:slab` handler used an in-memory cache with capacity-based eviction via `adlCache.keys().next().value`, which deletes the oldest insertion. Cache hits did not reposition the entry, so a hot slab inserted early would be evicted before cold slabs inserted later.
• Each cache miss is expensive (Solana RPC `fetchSlab` + full account parsing + ranking), so hot keys evicted under capacity pressure caused redundant RPC load and user-visible latency.
• Adds the same promotion-on-hit pattern already used in `src/routes/oracle-router.ts` (delete + reinsert before returning the cached payload). The eviction logic at the bottom of the handler is unchanged — it now effectively evicts the least-recently-used entry because the Map's iteration order tracks recency.

Test plan

• `npx tsc --noEmit` — clean
• Full test suite: 188/189 passing (the 1 failure is a pre-existing `tests/routes/prices.test.ts` issue on `main`, unrelated)

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📥 Commits

Reviewing files that changed from the base of the PR and between fb94c29 and 5f063f5.

📒 Files selected for processing (1)

• src/routes/adl.ts

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