feat: add username/password login, account settings, and changelog (#133) (#134)

- Add username/password login as additional auth mechanism alongside existing token
- First login must use token; password can be configured in Settings > Account
- Password login returns the existing static token (no auth middleware changes)
- Add account settings: setup, change password, change username, remove password
- Add logout button to sidebar footer
- Add version changelog popup (click version number in sidebar)
- Support all 8 locales (en, zh, de, es, fr, ja, ko, pt)
- Bump version to 0.4.3

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/client/src/data/changelog.ts

@@ -0,0 +1,23 @@
+export interface ChangelogEntry {
+  version: string
+  date: string
+  changes: string[]
+}
+
+export const changelog: ChangelogEntry[] = [
+  {
+    version: '0.4.3',
+    date: '2026-04-22',
+    changes: ['changelog.new_0_4_3_1', 'changelog.new_0_4_3_2', 'changelog.new_0_4_3_3', 'changelog.new_0_4_3_4'],
+  },
+  {
+    version: '0.4.2',
+    date: '2026-03-20',
+    changes: ['changelog.new_0_4_2_1', 'changelog.new_0_4_2_2', 'changelog.new_0_4_2_3', 'changelog.new_0_4_2_4', 'changelog.new_0_4_2_5'],
+  },
+  {
+    version: '0.4.1',
+    date: '2026-04-21',
+    changes: ['changelog.new_0_4_1_1'],
+  },
+]