resolver: multicall reads, keep-alive, workers and structured logs (#1883)

* resolver: queue up to 128 pending connections

* resolver: reuse connections to the node

* resolver: read each round in one multicall

* resolver: run worker processes, log durations

* resolver: keep smp-server connections alive

* resolver: test with pytest, lock dependencies

* resolver: structured logs and real client addresses

* resolver: refuse requests with a body

* resolver: harden pool, health and odd answers

* resolver: pin images, rotate logs

* resolver: stricter body check, redact RPC URL

* resolver: ship .env as .env.example

* resolver: pass settings from .env

* resolver: name the image snrc-resolve:local

scripts/resolver/.env.example

@@ -0,0 +1,32 @@
+# Copy to .env (next to docker-compose.yml) only to change a setting; without it
+# docker-compose.yml uses the values shown here.
+
+# ============================================================================
+# Chain settings.
+# ============================================================================
+
+# Ethereum network: mainnet (the SNRC `.testing` contracts live on mainnet)
+# or holesky (test). Mainnet full sync needs ~1 day and ~1.2 TB NVMe.
+NETWORK=mainnet
+
+# Beacon checkpoint-sync URL — used ONCE on first sync. Must expose the heavy
+# /eth/v2/debug/beacon/states/finalized endpoint (generic beacon APIs do not;
+# use a dedicated checkpoint provider). List: https://eth-clients.github.io/checkpoint-sync-endpoints/
+#   mainnet: https://mainnet-checkpoint-sync.attestant.io  (also beaconstate.info, sync-mainnet.beaconcha.in)
+#   holesky: https://checkpoint-sync.holesky.ethpandaops.io
+TRUSTED_NODE_URL=https://mainnet-checkpoint-sync.attestant.io
+
+# ============================================================================
+# Optional overrides — leave commented unless you need to change them.
+# ============================================================================
+
+# Nimbus NAT (default: any). For a stable public node set an explicit IP:
+#   NAT=extip:1.2.3.4        # your public IPv4: curl -s ifconfig.me
+
+# Resolver (defaults in the README's "Load and scaling" and "Logs" sections)
+#   SNRC_WORKERS=4                          # worker processes; default CPU count, at most 4
+#   SNRC_RPC_TIMEOUT=5                      # seconds per request to reth
+#   SNRC_LOG_FORMAT=json                    # default text (key=value)
+#   SNRC_LOG_COLOR=always                   # coloured `docker compose logs`
+#   SNRC_LOG_LEVEL=debug                    # also log health checks and idle connections
+#   SNRC_TRUSTED_PROXIES=172.16.0.0/12      # behind a reverse proxy on the host; see README