perf: cache /bounty, /logs/histogram, /deckies; bump /config TTL to 5s

Round-2 follow-up: profile at 500c/u showed _execute still dominating
the uncached read endpoints (/bounty 76%, /logs/histogram 73%,
/deckies 56%). Same router-level TTL pattern as /stats — 5s window,
asyncio.Lock to collapse concurrent calls into one DB hit.

- /bounty: cache default unfiltered page (limit=50, offset=0,
  bounty_type=None, search=None). Filtered requests bypass.
- /logs/histogram: cache default (interval_minutes=15, no filters).
  Filtered / non-default interval requests bypass.
- /deckies: cache full response (endpoint takes no params).
- /config: bump _STATE_TTL from 1.0 to 5.0 — admin writes are rare,
  1s was too short for bursts to coalesce at high concurrency.

tests/api/conftest.py

@@ -59,11 +59,17 @@ async def setup_db(monkeypatch) -> AsyncGenerator[None, None]:
     from decnet.web.router.stats import api_get_stats as _s
     from decnet.web.router.logs import api_get_logs as _l
     from decnet.web.router.attackers import api_get_attackers as _a
+    from decnet.web.router.bounty import api_get_bounties as _b
+    from decnet.web.router.logs import api_get_histogram as _lh
+    from decnet.web.router.fleet import api_get_deckies as _d
     _h._reset_db_cache()
     _c._reset_state_cache()
     _s._reset_stats_cache()
     _l._reset_total_cache()
     _a._reset_total_cache()
+    _b._reset_bounty_cache()
+    _lh._reset_histogram_cache()
+    _d._reset_deckies_cache()
 
     # Create schema
     async with engine.begin() as conn: