feat(todo): the server finds places through the instance's Photon (ADR 0033, D32)

Todo's locations search through the person's own instance, as Train's
planner does, not a public service: `SearchEndpoint` on `PlaceSearch`, for
those signed in, 60 searches a minute, nothing kept or logged. Its `Place`
carries the address's parts and the object in OpenStreetMap, and a shop's
car park or charger is left out, which came first for `Lindau EDEKA`.

`compose.todo-search.yaml` puts Todo's server on compose.search.yaml's
Photon. A file of its own: without it Todo starts as it did, and offers no
search.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/sidecars/README.md

@@ -24,6 +24,7 @@ site changes.
 | Train's own map tiles, beside Train | `compose.maps.yaml` | `train-maps.caddy` (in Train's site) |
 | Photon, which finds places for Train's route planner, beside Train | `compose.search.yaml` | none |
 | Halkyon Todo's server | `compose.todo.yaml` | `todo.caddy` |
+| Todo's place search, on Train's Photon | `compose.todo-search.yaml` | none |
 
 Both together: `COMPOSE_FILE=compose.learn.yaml:compose.jellyfin.yaml:compose.languagetool.yaml`.
 
@@ -519,3 +520,10 @@ Steps, in order:
    instance is away for seconds. Todo's server applies its migrations as it starts.
 5. **Check it**: `https://todo.halkyon.eu/` answers; in Todo, signed in with a Learn
    account, a task added on one device shows on another.
+6. **Place search** (optional; ADR 0033, D32): Todo's locations find places through the
+   Photon of *Train's search*, set up first. In `deploy/.env`,
+   `compose.todo-search.yaml` added to `COMPOSE_FILE` after `compose.todo.yaml` and
+   `compose.search.yaml`, then `docker compose up -d`, which recreates Todo's server
+   alone. Without it Todo starts as it did, and its app offers no search. Nothing
+   searched is kept or logged, and a task's location stays sealed on the person's
+   devices.