fix(notices): keep the release modal up across the whole 4.x line

The 4.0.0 notice was scoped to a 4.0.x window on the assumption that each
release would bring its own entry. 4.1.0 shipped without one, so the modal
switched itself off and nothing took its place: the thank-you notice it
replaced is retired below 4.0.0, leaving a 4.1 install with no notice at all.

Hold it open to the 5.0.0 boundary instead. What it introduces is the 4.x
line, which is still what somebody arriving on 4.1 or 4.2 is meeting for the
first time, and a later major gets its own entry the way this one did.

server/src/systemNotices/registry.ts

@@ -106,11 +106,14 @@ export const SYSTEM_NOTICES: SystemNotice[] = [
     conditions: [{ kind: 'managed', is: false }],
     publishedAt: '2026-08-22T00:00:00Z',
     priority: 110,
-    // The 4.0.x window. The copy is about this release, so somebody arriving on
-    // 4.1 — or jumping 3.x straight to 4.2 — should get that release's notice
-    // instead of this one, not a summary of a version they skipped.
+    // The whole 4.x line. The copy is about what 4.0.0 brought, and that is still
+    // what somebody arriving anywhere on 4.x is being introduced to — the minor
+    // releases after it add to that picture rather than replace it. Held open to
+    // the 5.0.0 boundary (exclusive) so a 4.1/4.2 install is not left with no
+    // notice at all, which is what a per-release window did the moment 4.1.0
+    // shipped without an entry of its own.
     minVersion: '4.0.0',
-    maxVersion: '4.1.0',
+    maxVersion: '5.0.0',
   },
 
   // ── Thank-you + support the project — shown once per install AND once per upgrade ──