Phase 4: real per-tenant ClickHouse isolation via a new enterprise-api binary

Closes the threat model's headline finding for the SQL query path:
enterprise/internal/tenantprovision does real CREATE DATABASE/USER/GRANT
against ClickHouse, and enterprise/internal/chrunner is a per-tenant
connection registry implementing api's SQLRunner interface, resolving
the tenant from the authenticated request identity -- never a
caller-suppliable parameter. Both are wired into a new binary,
enterprise/cmd/enterprise-api, alongside the unchanged single-tenant
api/cmd/api, since AGPL core can never import enterprise/ and Go's own
internal/ package visibility rules meant enterprise/ couldn't implement
core's SQLRunner interface without importing the package that defines
it. That required moving api/internal/{authz,queryapi,dashboards,
querylang/executor,searchclient,httpserver} out of internal/ -- the
minimal set enterprise-api needs to import; querylang's compiler
internals (planner/lexer/parser/ast/ir) and api's own config stay
internal, since nothing outside api needs them directly.

Also finally wires enterprise/internal/audit into queryapi.AuditLogger
(nil since Phase 4 task 4) via a new adapter, and adds live-ClickHouse
integration tests for two of the four adversarial probes named in
docs/phase-4-isolation-design.md's verification plan.

Corrected several overclaims in the docs while writing this up: an
earlier claim that rbacstore's CRUD was "verified against a live
Postgres" was never actually true in this environment (only
internal/audit was, earlier in this phase, before Docker access was
lost) -- threat-model.md, phase-4-runbook.md, CLAUDE.md, and
enterprise/README.md all now distinguish "a real integration test
exists" from "this was confirmed against a live database."

Still not built: Tantivy/free-text tenant isolation
(enterprise/internal/searchclient), and any deployment-topology
mechanism that actually routes traffic to enterprise-api instead of
plain api -- both binaries exist side by side today with nothing
enforcing or flagging which one a deployment runs.

enterprise/internal/audit/queryapi_adapter.go

@@ -0,0 +1,76 @@
+// Adapts *Store to api/queryapi.AuditLogger -- the interface core
+// defines and has carried as a nil-by-default field
+// (api/queryapi.Handler.audit) since Phase 4 task 4, waiting on exactly
+// this: a real implementation, wired in by enterprise/cmd/enterprise-api
+// (the one binary allowed to import both packages -- see chrunner's doc
+// comment on the enterprise->api import direction).
+package audit
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/sentry/sentry/api/authz"
+	"github.com/sentry/sentry/api/queryapi"
+)
+
+// QueryAPILogger implements queryapi.AuditLogger by translating its
+// tenant-agnostic QueryAuditEntry into this package's Entry, reading
+// tenant/user identity from ctx -- exactly the shape
+// queryapi.AuditLogger's doc comment describes: "an enterprise-side
+// implementation reads identity from ctx rather than this interface
+// growing tenant-awareness."
+type QueryAPILogger struct {
+	store  *Store
+	source Source
+}
+
+// NewQueryAPILogger wraps store for use as a specific Source -- api's
+// queryapi.Handler and /alerting's evaluations go through different
+// enterprise-api-fronted paths today (SourceAPI is the only one
+// actually wired to a real HTTP handler; SourceAlerting is named for
+// when alerting's queries get audited the same way, not yet built).
+func NewQueryAPILogger(store *Store, source Source) *QueryAPILogger {
+	return &QueryAPILogger{store: store, source: source}
+}
+
+func (l *QueryAPILogger) LogQuery(ctx context.Context, entry queryapi.QueryAuditEntry) error {
+	identity, ok := authz.IdentityFromContext(ctx)
+	if !ok || identity.TenantID == "" {
+		// Fail open at the queryapi.Handler call site already covers
+		// "don't take down the query path" -- this specific error tells
+		// that fail-open path *why* the write didn't happen, distinct
+		// from a real audit-storage failure, since chrunner.RunSQL
+		// would already have refused the query itself in this case (see
+		// that package's RunSQL) -- this branch mostly protects against
+		// a future caller that skips chrunner's own check.
+		return fmt.Errorf("audit: no tenant identity in context, refusing to write an unattributable audit entry")
+	}
+
+	status := StatusSuccess
+	var errMsg *string
+	if !entry.Success {
+		status = StatusError
+		errMsg = &entry.Error
+	}
+	var userID *string
+	if identity.UserID != "" {
+		userID = &identity.UserID
+	}
+	queryText := entry.Query
+	rowCount := entry.RowCount
+	durationMS := int(entry.Duration.Milliseconds())
+
+	_, err := l.store.Append(ctx, Entry{
+		TenantID:     identity.TenantID,
+		UserID:       userID,
+		Source:       l.source,
+		EventType:    EventQuery,
+		QueryText:    &queryText,
+		RowCount:     &rowCount,
+		DurationMS:   &durationMS,
+		Status:       status,
+		ErrorMessage: errMsg,
+	})
+	return err
+}