feat: scaffold travel-memories Flask app and test infrastructure

Adds services/travel-memories/ with Flask factory (create_app), stub
route blueprints, pytest/playwright smoke test infra (httpserver session
fix, pytest.ini pythonpath), phase2–6 fixture JSONs, Dockerfile, and
docker-compose service entry. Smoke test (test_health) passes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/travel-memories/tests/fixtures/phase4_state.json

@@ -0,0 +1,16 @@
+{
+  "album_id": "album-1",
+  "album_name": "Central Asia 2023",
+  "grav_trip_slug": "central-asia-2023",
+  "phase": "group",
+  "phases_completed": ["triage", "curate"],
+  "phase_stale": [],
+  "photos": [
+    {"id": "asset-1", "original_filename": "IMG_001.jpg",
+     "local_datetime": "2023-09-05T09:03:00", "tag": "journal", "order": 0},
+    {"id": "asset-2", "original_filename": "IMG_002.jpg",
+     "local_datetime": "2023-09-05T14:30:00", "tag": "story", "order": 1}
+  ],
+  "groups": [],
+  "notes": "I remember the airport was chaos."
+}