Language and theme follow the account: PATCH /me for the theme, /me's language by default

The server's /api/v2 now has PATCH /me {language, theme} and /me lists its languages and
themes. The theme is the account's and choosing one saves it there (a refusal is said);
a server whose /me lists no themes keeps the earlier choice in the app. The language is the
account's unless Settings chose this computer's or another (kept in the app, as the phone
does); a change of the account's opens the window again in it, once.

Fixtures re-pinned to the server's dev (f7f2ff2), with the new /api/v2 parity ones.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/fetch-fixtures.sh

@@ -14,7 +14,9 @@ SERVER="${LEMBAS_SERVER:-../LLeMbas}"
 FROM="tests/fixtures/api_v2"
 OUT="tests/ui/fixtures"
 FILES="chat_agent.json event_ask.json event_status.json event_status_idle.json event_status_person.json
-event_status_stopped.json event_tree.json models_agent.json subagent_findings.json subagent_transcript.json tree.json"
+event_status_stopped.json event_tree.json models_agent.json subagent_findings.json subagent_transcript.json tree.json
+me.json folders.json folder.json search.json memories.json memory.json scope.json push_schedule.json push_schedule_failed.json
+event_schedules.json schedule_run.json chat.json chats_listed.json files_listing.json"
 
 [ $# -eq 1 ] || { echo "usage: scripts/fetch-fixtures.sh <server-ref>" >&2; exit 2; }
 commit="$(git -C "$SERVER" rev-parse --verify --quiet "$1^{commit}")" \