refactor(node): split into config, sequencer, and full crates

[kariy]

Split katana-node into three separate crates under crates/node/: katana-node-config for shared config types (db, rpc, metrics), katana-sequencer-node for the sequencer node, and katana-full-node for the full node. Shared configs are re-exported from each node crate so consumers access them through a single path. All downstream crates (cli, utils, rpc-server, tests/snos) updated accordingly. Replaces katana_rpc_server::cors::HeaderValue with http::HeaderValue in shared config to avoid coupling config to the RPC server implementation.

crates/node/
├── config/     → katana-node-config     (shared: db, rpc, metrics)
├── sequencer/  → katana-sequencer-node  (sequencer node)
└── full/       → katana-full-node       (full node)

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