Rename the identifiers that carried the upstream name

Everything clients, users and operators meet now carries the fork's name,
with no aliases (SPEC.md §2.4, changed here from "protocol identifiers
stay"):

- JMAP: upstream's registry capability is urn:inbuxa:jmap:registry, beside
  the fork's own urn:inbuxa:jmap.
- WebDAV lock and sync tokens are urn:inbuxa:dav*; clients resync once.
- Sieve: vnd.inbuxa.while and vnd.inbuxa.expressions. sieve-rs spells these
  into its compiler, so it's vendored (vendor/sieve-rs, 0.7.3) and patched in;
  a unit test fails if Cargo.lock ever moves past the vendored copy. The
  trusted runtime now names itself too, rather than answering sieve-rs's
  default.
- The web interface's OAuth client is inbuxa-webui. On every start the old
  stalwart-webui client is removed and any application naming it is moved
  over.
- The spam filter's blobs are INBUXA_SPAM_*; every start moves any left
  under the old keys, so a trained model survives.
- SQL stores and log files default to inbuxa, in the code and in the
  schema served to the admin (checksum regenerated).
- Settings are INBUXA_* only. A STALWART_* variable that's set where its
  INBUXA_* one isn't stops the server at startup, naming it.
- The version-upgrade messages link docs.inbuxa.org's migration page, and
  the OpenAPI description, smtp crate metadata and web-push test fixtures
  lose the name.

Kept on purpose, allowlisted with reasons: the OAuth key-derivation
contexts (renaming them would end every session and invalidate every
sealed client id) and the hashed application prefix.

Also fixes a latent start-up failure: ensure_client updated an existing
first-party client with a revision of 0, which the registry's assertion
never matches, so adding a redirect URI or changing the webmail secret
failed start-up. And the principal session test now expects
legacyProtocols (C-1, added 2026-09-21), which it had missed.

Tested: the server builds without warnings; common's 106 unit tests,
including the vendoring check; a new integration test for the two
start-up migrations; and the webdav, jmap, imap and SMTP Sieve suites.

crates/registry/src/schema/structs_impl.rs

@@ -29622,8 +29622,8 @@ impl Default for MySqlSettings {
         Self {
             host: Default::default(),
             port: 3306u64,
-            database: "stalwart".to_string(),
-            auth_username: Some("stalwart".to_string()),
+            database: "inbuxa".to_string(),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
         }
     }
@@ -29780,8 +29780,8 @@ impl Default for MySqlStore {
             read_replicas: Default::default(),
             host: Default::default(),
             port: 3306u64,
-            database: "stalwart".to_string(),
-            auth_username: Some("stalwart".to_string()),
+            database: "inbuxa".to_string(),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
         }
     }
@@ -29942,7 +29942,7 @@ impl Default for NatsCoordinator {
             no_echo: true,
             use_tls: false,
             auth_secret: Default::default(),
-            auth_username: Some("stalwart".to_string()),
+            auth_username: Some("inbuxa".to_string()),
             credentials: Default::default(),
         }
     }
@@ -31125,8 +31125,8 @@ impl Default for PostgreSqlSettings {
         Self {
             host: Default::default(),
             port: 5432u64,
-            database: "stalwart".to_string(),
-            auth_username: Some("stalwart".to_string()),
+            database: "inbuxa".to_string(),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
             options: Default::default(),
         }
@@ -31270,8 +31270,8 @@ impl Default for PostgreSqlStore {
             read_replicas: Default::default(),
             host: Default::default(),
             port: 5432u64,
-            database: "stalwart".to_string(),
-            auth_username: Some("stalwart".to_string()),
+            database: "inbuxa".to_string(),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
             options: Default::default(),
         }
@@ -32576,7 +32576,7 @@ impl Default for RedisClusterStore {
         Self {
             urls: Map::new(vec!["redis://127.0.0.1".to_string()]),
             timeout: Duration::from_millis(10000),
-            auth_username: Some("stalwart".to_string()),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
             max_retry_wait: Default::default(),
             min_retry_wait: Default::default(),
@@ -32743,7 +32743,7 @@ impl Default for RedisSentinelStore {
             urls: Map::new(vec!["redis://127.0.0.1:26379".to_string()]),
             service_name: "mymaster".to_string(),
             timeout: Duration::from_millis(10000),
-            auth_username: Some("stalwart".to_string()),
+            auth_username: Some("inbuxa".to_string()),
             auth_secret: Default::default(),
             sentinel_username: Default::default(),
             sentinel_secret: Default::default(),
@@ -46308,7 +46308,7 @@ impl Default for TracerLog {
     fn default() -> Self {
         Self {
             path: Default::default(),
-            prefix: "stalwart".to_string(),
+            prefix: "inbuxa".to_string(),
             rotate: LogRotateFrequency::Daily,
             ansi: true,
             multiline: false,