PCAP import always fails: importer INSERT is rejected by the node's read-only SQL validator (11.0.336) #993

Summary

POST /api/v4/imports/pcap always fails with a 400. The importer builds an
INSERT, sends it to the storage node's HTTP /query endpoint, and that
endpoint rejects any statement that is not SELECT/WITH/SHOW/DESCRIBE/EXPLAIN/PRAGMA.
The PCAP import feature therefore cannot work in any configuration.

Reproduced on 11.0.336 (ghcr.io/sipcapture/homer:latest, commit 93fdb78),
all-in-one deployment with local DuckLake storage (sqlite catalog, no S3).

Reproduction

curl -X POST http://localhost:8080/api/v4/imports/pcap \
  -H "Authorization: Bearer $TOKEN" \
  -F "file=@capture.pcap" \
  -F "override_to_current_time=true"

Response:

{"error":{"type":"https://api.homer/errors/invalid_argument","title":"Bad Request","status":400,
"detail":"query HTTP error: status=400 body=\"{\\\"success\\\":false,\\\"error\\\":\\\"SQL validation failed: query must start with SELECT, WITH, SHOW, DESCRIBE, EXPLAIN, or PRAGMA (got \\\\\\\"INSERT\\\\\\\")\\\"}\\n\""}}

The same happens from the UI import dialog.

Cause

1. importPcapSIP builds an INSERT via BuildInsertMultiValues and executes it
   with flight.QueryFirstConnected — src/coordinator/handlers/pcap_sip_import.go:167-172.
2. QueryFirstConnected is documented as "Intended for INSERT/DDL that must not be
   duplicated across a multi-node cluster" — src/coordinator/services/flight_service.go:283-285.
3. It delegates to queryNode, which is HTTP-only and always posts to the node's
   /query endpoint on FlightServer.Port + 1 — src/coordinator/services/flight_service.go:445-453.
   There is no gRPC/Airport write path to fall back to.
4. Node.handleQuery calls sqlvalidator.ValidateRawSQL(req.SQL) unconditionally,
   before any branching — src/node/node.go:1215. allowedStatementStarts permits
   only SELECT/WITH/SHOW/DESCRIBE/EXPLAIN/PRAGMA, so INSERT is rejected with 400
   (src/coordinator/sqlvalidator/validator.go:276).

The validator was added for GHSA-rm5w-rqr7-2h54 (per the comment on node.go:1214).
It appears the import path was not accounted for.

Supporting evidence that DML was intended on this endpoint: immediately after the
validator, handleQuery still contains a non-SELECT branch that calls
db.ExecContext(...) (src/node/node.go:1230). That branch is now unreachable —
nothing can get past ValidateRawSQL and still be a non-SELECT statement.

Impact

• PCAP import is non-functional for all users on this release, via API and UI.
• No workaround via configuration: there is no allow_write / read_only toggle
  for the node, and queryNode has a single hard-coded HTTP transport.
• Normal HEP ingest is unaffected — the writer holds its own DuckLake connection
  and does not go through the node's /query endpoint.

Suggested fix

Give internal writes a path that bypasses the raw-SQL validator, rather than
relaxing the validator itself. For example an authenticated internal write
endpoint/RPC used by QueryFirstConnected, keeping /query read-only for
user-supplied SQL. The dead ExecContext branch in handleQuery should then be
removed or moved to that path.

Environment