Import upstream v0.16.24, stripped

Upstream commit: af37a234981722493b74623a983581691d2b70b6
Enterprise-only files removed or emptied: 63
Enterprise-only snippets removed: 118 in 50 files
Dangling module declarations removed: 5
Edits turning enterprise off: 25
Third-party code: 14 files, 0 not in THIRD-PARTY.md
Renamed identifiers: 62 in 18 files
Verification: clean

The same Enterprise footprint as v0.16.23. The build check fails only on
tests/src/directory/issuer.rs, unchanged since v0.16.23: it calls a helper
from upstream's Enterprise-only OIDC test, and tests issuer-based directory
routing, an Enterprise feature. main has never carried it.

crates/jmap-proto/src/references/resolve.rs

@@ -338,6 +338,10 @@ impl ResolveReference for ImportEmailRequest {
     fn resolve_references(&mut self, response: &Response<'_>) -> trc::Result<()> {
         // Resolve email mailbox references
         for email in self.emails.values_mut() {
+            if let MaybeIdReference::Reference(ir) = &email.blob_id {
+                email.blob_id = MaybeIdReference::Id(response.eval_blob_id_reference(ir)?);
+            }
+
             match &mut email.mailbox_ids {
                 MaybeResultReference::Reference(reference) => {
                     email.mailbox_ids = MaybeResultReference::Value(