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/main/Cargo.toml

@@ -7,7 +7,7 @@ homepage = "https://stalw.art"
 keywords = ["imap", "jmap", "smtp", "email", "mail", "webdav", "server"]
 categories = ["email"]
 license = "AGPL-3.0-only OR LicenseRef-SEL"
-version = "0.16.23"
+version = "0.16.24"
 edition = "2024"
 
 [[bin]]