feat(system-notices): replace expiresAt with [minVersion, maxVersion) version gate

Prevents users who upgrade across multiple versions from seeing all
interim notices at once. Version bounds are evaluated server-side using
semver.coerce so prerelease builds compare as their base release.
Range is lower-inclusive, upper-exclusive: maxVersion: '4.0.0' hides
the notice once 4.0.0 ships.

server/tests/unit/systemNotices/registry.test.ts

@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import fs from 'node:fs';
 import path from 'node:path';
+import semver from 'semver';
 import { SYSTEM_NOTICES } from '../../../src/systemNotices/registry.js';
 
 /** Collect all actionIds registered via registerNoticeAction() in client source files. */
@@ -45,4 +46,21 @@ describe('registry integrity', () => {
       expect(() => new Date(n.publishedAt).toISOString()).not.toThrow();
     }
   });
+
+  it('minVersion and maxVersion are valid semver when set, and minVersion <= maxVersion when both set', () => {
+    for (const n of SYSTEM_NOTICES) {
+      if (n.minVersion !== undefined) {
+        expect(semver.valid(n.minVersion), `notice "${n.id}" has invalid minVersion "${n.minVersion}"`).not.toBeNull();
+      }
+      if (n.maxVersion !== undefined) {
+        expect(semver.valid(n.maxVersion), `notice "${n.id}" has invalid maxVersion "${n.maxVersion}"`).not.toBeNull();
+      }
+      if (n.minVersion && n.maxVersion) {
+        expect(
+          semver.lte(n.minVersion, n.maxVersion),
+          `notice "${n.id}": minVersion ${n.minVersion} > maxVersion ${n.maxVersion}`
+        ).toBe(true);
+      }
+    }
+  });
 });

server/tests/unit/systemNotices/versionRange.test.ts

@@ -0,0 +1,56 @@
+import { describe, it, expect } from 'vitest';
+import { isNoticeVersionActive } from '../../../src/systemNotices/service.js';
+import type { SystemNotice } from '../../../src/systemNotices/types.js';
+
+const base: SystemNotice = {
+  id: 'test-notice',
+  display: 'modal',
+  severity: 'info',
+  titleKey: 'k',
+  bodyKey: 'k',
+  dismissible: true,
+  conditions: [],
+  publishedAt: '2026-01-01T00:00:00Z',
+};
+
+describe('isNoticeVersionActive', () => {
+  it('passes when no bounds are set', () => {
+    expect(isNoticeVersionActive(base, '3.5.0')).toBe(true);
+  });
+
+  it('passes when app version equals minVersion (inclusive)', () => {
+    expect(isNoticeVersionActive({ ...base, minVersion: '3.0.0' }, '3.0.0')).toBe(true);
+  });
+
+  it('fails when app version is below minVersion', () => {
+    expect(isNoticeVersionActive({ ...base, minVersion: '3.0.0' }, '2.9.9')).toBe(false);
+  });
+
+  it('fails when app version equals maxVersion (exclusive upper bound)', () => {
+    expect(isNoticeVersionActive({ ...base, maxVersion: '3.0.0' }, '3.0.0')).toBe(false);
+  });
+
+  it('fails when app version exceeds maxVersion', () => {
+    expect(isNoticeVersionActive({ ...base, maxVersion: '3.0.0' }, '3.0.1')).toBe(false);
+  });
+
+  it('passes when app version is just below maxVersion', () => {
+    expect(isNoticeVersionActive({ ...base, maxVersion: '3.0.0' }, '2.9.9')).toBe(true);
+  });
+
+  it('passes when app version is inside [minVersion, maxVersion)', () => {
+    expect(isNoticeVersionActive({ ...base, minVersion: '3.0.0', maxVersion: '3.9.9' }, '3.5.2')).toBe(true);
+  });
+
+  it('treats prerelease app version as base release (semver.coerce)', () => {
+    expect(isNoticeVersionActive({ ...base, minVersion: '3.0.0' }, '3.0.0-pre.42')).toBe(true);
+  });
+
+  it('skips notice and returns false when minVersion is invalid semver', () => {
+    expect(isNoticeVersionActive({ ...base, minVersion: 'not-semver' }, '3.0.0')).toBe(false);
+  });
+
+  it('skips notice and returns false when maxVersion is invalid semver', () => {
+    expect(isNoticeVersionActive({ ...base, maxVersion: 'garbage' }, '3.0.0')).toBe(false);
+  });
+});