feat: v6.0.0 PWA offline support

- manifest + icones, service worker (precache, network-first, Background Sync)

- module client FlowOffline (IndexedDB, queue, delta, flush) + hook editeur

- endpoints /api/v2/sync/{delta,batch,status} + moteur de sync (conflits LWW/orpheline/copie offline)

- migrations offline_sync_queue + sync_version (triggers)

- UI offline (banner, badge sync, toasts, icone dirty) + doc /help

- tests pytest (sync, migrations, SW, offline) + E2E Playwright; bump 6.0.0

tests/test_app.py

@@ -1024,6 +1024,25 @@ def test_pwa_manifest(client):
     data = resp.json()
     assert data["name"] == "FlowDeck"
     assert data["display"] == "standalone"
+    assert any(i.get("sizes") == "192x192" for i in data["icons"])
+
+
+def test_pwa_manifest_static_assets():
+    """v6.0.0: the static manifest and every referenced icon must exist on disk."""
+    import json
+    from pathlib import Path
+
+    root = Path(__file__).resolve().parent.parent
+    manifest_path = root / "static" / "manifest.json"
+    assert manifest_path.is_file(), "static/manifest.json missing"
+
+    manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
+    assert manifest["name"] == "FlowDeck"
+    assert "icons" in manifest and len(manifest["icons"]) >= 8
+
+    for icon in manifest["icons"]:
+        src = icon["src"].lstrip("/")
+        assert (root / src).is_file(), f"icon missing: {src}"
 
 
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