fix(pgwire): answer kv writes with one INSERT tag

[EnRaiha]

Summary

kv INSERT and PUT writes reported no affected count, so pgwire emitted a bare OK; a client reads that as zero rows written. Separately, routed response-shaper errors were flattened to XX000 at each pgwire shaper call site even when the error already carried a classifying numeric code.

• report affected = 1 in execute_kv_insert and execute_kv_put, and map KvOp::Insert, KvOp::Put, KvOp::BatchPut to the INSERT tag (response_shape/types.rs, kv/crud/write_basic.rs);
• route the pgwire shaper call sites through numeric_code_to_sqlstate (pgwire/types/error_map.rs plus the six routing sites) and add the read-path arms it was missing: UNDEFINED_OBJECT, OBJECT_NOT_READY, NOT_FOUND, DATABASE_NOT_FOUND, SQL_NOT_ENABLED, TYPE_MISMATCH, OVERFLOW.

Red proof (the test fails on main without the fix)

panicked at nodedb/tests/wire/cases/sql_dml_affected_counts.rs:302:5:
assertion `left == right` failed: a KV INSERT that wrote one key must report 1, not a bare tag the client reads as 0
  left: 0
 right: 1

Validation (local, on this branch)

Check	Result
the four tests in this PR (error_map ×2, kv affected counts ×2)	4 passed
cargo fmt --all	clean
cargo clippy -p nodedb --all-targets --all-features --profile ci -- -D warnings	clean
repository hygiene gate (test registry, comment and commit hygiene, module contracts)	pass

One commit; no changes outside the files listed above.

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