Invalidate weekplan cache after plan mutations (add/remove/move)

[TheTrustedAdvisor]

Problem

After successful plan add, plan remove, or plan move operations, the local weekplan cache (cookidoo_weekplan_raw.json) is not updated. This means:

tmx plan add r123456 --date 2026-04-20  # ✅ Added on server
tmx plan show                            # ❌ Shows stale data without the new recipe
tmx plan sync                            # Must manually sync to see changes

The user sees contradictory output — the add succeeds but the show doesn't reflect it.

Proposed Solution

After each successful mutation in cmd_plan_add, cmd_plan_remove, and cmd_plan_move, either:

Option A (simple): Delete the cache and inform the user:

if success:
    WEEKPLAN_JSON.unlink(missing_ok=True)
    print(f"✅ {message}")
    print("  (Cache gelöscht — 'tmx plan show' wird automatisch neu laden)")

Option B (better UX): Auto-sync after mutation:

if success:
    print(f"✅ {message}")
    cmd_plan_sync(args, quiet=True)

Option A is simpler and triggers a sync only when the user actually runs plan show (which already has auto-sync-on-missing-cache logic at line 1413).

Impact

• Effort: Trivial (3 lines per command)
• User impact: Eliminates confusing stale data after mutations