refactor(security): move all database access into pkg/security/lookup

pkg/security no longer contains SQL. Every provider calls a store interface
from lookup, implemented by a procedure backend (Postgres stored procedures,
the default there) and a direct backend (dialect-driven SQL for postgres,
sqlite, mysql and mssql with configurable table and column names).

- add sectypes, lookup, lookup/{dialect,procedure,direct,backends,ddl,conformance}
- split totp and providers sub packages out of the core package
- replace SQLNames/TableNames/QueryMode with lookup.Config (see breaking_changes.md)
- direct backend now covers column/row security and API-key login
- move txsettings SQL to lookup.ApplyTxSettings; remove password.go
- move schema scripts under lookup/, add reference DDL per dialect
- add a shared conformance suite; run it on sqlite, and on Postgres in a
  podman/docker container (RESOLVESPEC_TEST_CONTAINERS=1)
- fix procedure schema bugs found on real Postgres: duplicate p_data
  parameter, JSON null arrays, expires_at timezone casts, passkey list
  GROUP BY, missing resolvespec_passkey_login; accept zone-less timestamps

pkg/common/interfaces.go

@@ -2,6 +2,7 @@ package common
 
 import (
 	"context"
+	"database/sql"
 	"encoding/json"
 	"io"
 	"net/http"
@@ -38,6 +39,15 @@ type Database interface {
 	DriverName() string
 }
 
+// SQLDBProvider is implemented by adapters that wrap a *sql.DB (directly or through an ORM).
+// It lets packages that work on database/sql, such as pkg/security/lookup, reuse the
+// connection an application already configured. Transaction adapters do not implement it.
+type SQLDBProvider interface {
+	// SQLDB returns the current underlying *sql.DB. After an adapter reconnects it
+	// returns the new handle, so do not cache it across reconnects.
+	SQLDB() *sql.DB
+}
+
 // SelectQuery interface for building SELECT queries (compatible with both GORM and Bun)
 type SelectQuery interface {
 	Model(model interface{}) SelectQuery