fix: pass host timezone to container and reject UTC-suffixed timestamps (#371)

Containers had no TZ set, so any time-aware code inside ran in UTC while
the host interpreted bare timestamps as local time. Now TIMEZONE from
config.ts is passed via -e TZ= to the container args.

Also rejects Z-suffixed or offset-suffixed timestamps in the container's
schedule_task validation, since bare timestamps are expected to be local
time and silently accepting UTC suffixes would cause an offset mismatch.

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

src/container-runner.test.ts

@@ -14,6 +14,7 @@ vi.mock('./config.js', () => ({
   DATA_DIR: '/tmp/nanoclaw-test-data',
   GROUPS_DIR: '/tmp/nanoclaw-test-groups',
   IDLE_TIMEOUT: 1800000, // 30min
+  TIMEZONE: 'America/Los_Angeles',
 }));
 
 // Mock logger