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/app/routes/proxy.py

@@ -1,3 +1,29 @@
-from flask import Blueprint
+from flask import Blueprint, current_app, Response, abort
+from app.immich import ImmichClient
 
 bp = Blueprint("proxy", __name__)
+
+
+def _client() -> ImmichClient:
+    return ImmichClient(
+        base_url=current_app.config["IMMICH_URL"],
+        api_key=current_app.config["IMMICH_API_KEY"],
+    )
+
+
+@bp.get("/proxy/thumb/<asset_id>")
+def thumb(asset_id):
+    try:
+        data = _client().get_thumbnail(asset_id)
+    except ConnectionError:
+        abort(502)
+    return Response(data, content_type="image/jpeg")
+
+
+@bp.get("/proxy/original/<asset_id>")
+def original(asset_id):
+    try:
+        data = _client().get_original(asset_id)
+    except ConnectionError:
+        abort(502)
+    return Response(data, content_type="image/jpeg")