SEV-378: add tolerant formatDate/formatDateTime to shared (v0.3.0)

Our Go/Turso layer emits SQLite datetime('now') as "YYYY-MM-DD HH:MM:SS"
(UTC, no zone), which new Date() can't parse → "Invalid Date" in admin.
formatDate/formatDateTime normalize that shape (space→T + Z) and RFC3339,
returning '' for falsy/invalid. Tests cover both formats + empties.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@switchev/web-shared",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "Shared browser helpers (formatters, markdown, image polling) for the SwitchEV frontends",
   "type": "module",
   "exports": {