feat: add Immich API client and photo proxy routes

Implements ImmichClient with list_albums, get_album, get_thumbnail,
get_original methods; wraps connection errors as ConnectionError.
Adds /proxy/thumb/<asset_id> and /proxy/original/<asset_id> Flask routes.

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

services/travel-memories/tests/test_immich.py

@@ -0,0 +1,50 @@
+import pytest
+from app.immich import ImmichClient
+
+
+@pytest.fixture
+def client(mock_immich):
+    return ImmichClient(
+        base_url=f"http://127.0.0.1:8099",
+        api_key="test-key",
+    )
+
+
+def test_list_albums(client):
+    albums = client.list_albums()
+    assert len(albums) == 1
+    assert albums[0]["albumName"] == "Central Asia 2023"
+
+
+def test_get_album(client):
+    album = client.get_album("album-1")
+    assert len(album["assets"]) == 3
+
+
+def test_get_thumbnail_returns_bytes(client):
+    data = client.get_thumbnail("asset-1")
+    assert isinstance(data, bytes)
+    assert len(data) > 0
+
+
+def test_get_original_returns_bytes(client):
+    data = client.get_original("asset-1")
+    assert isinstance(data, bytes)
+
+
+def test_list_albums_connection_error_raises(monkeypatch):
+    client = ImmichClient(base_url="http://127.0.0.1:1", api_key="x")
+    with pytest.raises(ConnectionError):
+        client.list_albums()
+
+
+def test_proxy_thumb_route(base_url, page, seed_state):
+    seed_state("phase2_state")
+    page.goto(f"{base_url}/proxy/thumb/asset-1")
+    assert page.evaluate("document.contentType").startswith("image/")
+
+
+def test_proxy_original_route(base_url, page, seed_state):
+    seed_state("phase2_state")
+    page.goto(f"{base_url}/proxy/original/asset-1")
+    assert page.evaluate("document.contentType").startswith("image/")