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.

tests/src/jmap/principal/get.rs

@@ -244,7 +244,7 @@ pub async fn test(test: &TestServer) {
               "webWriteUrlTemplate": null
             },
             "urn:ietf:params:jmap:mail:share": {},
-            "urn:stalwart:jmap": {}
+            "urn:inbuxa:jmap:registry": {}
           }
         }
       },
@@ -265,7 +265,7 @@ pub async fn test(test: &TestServer) {
         "urn:ietf:params:jmap:principals:availability": john_id,
         "urn:ietf:params:jmap:filenode": john_id,
         "urn:ietf:params:jmap:mail:share": john_id,
-        "urn:stalwart:jmap": john_id
+        "urn:inbuxa:jmap:registry": john_id
       },
       "username": "[email protected]",
       "apiUrl": "https://127.0.0.1:8899/jmap/",