feat: add version display on login page and sidebar (v1.4.0)

- Login page: shows "vX.Y.Z | Core: vA.B.C" at bottom of card
- Sidebar footer: shows version when expanded
- Calls GET /api/v1/version (no auth required)
- For field engineers to instantly identify platform version

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

VERSIONS.json

@@ -1,7 +1,7 @@
 {
   "project": "ems-frontend-template",
-  "project_version": "1.3.0",
-  "core_version": "1.3.0",
+  "project_version": "1.4.0",
+  "core_version": "1.4.0",
   "last_updated": "2026-04-06",
-  "notes": "Generic branding, removed all Tianpu-specific hardcoding"
+  "notes": "Version display on login + sidebar for field engineers"
 }