halkyon_app: data locations as precise as a country or a state

An operator's DATA_LOCATION and BACKUP_LOCATION may name a subdivision
(ISO 3166-2, US-CA, DE-BY) besides the EU or a country. The app adds
"(EU)" to a member country and the country to a subdivision ("Germany
(EU)", "California, United States", "Bavaria, Germany (EU)"), in
English and German, and shows the most specific flag there is: a
subdivision's own where the flag package has one, else its country's.
Subdivision names come from Unicode CLDR 48.2 (tool/subdivision_names.py),
bundled with their licence, which the app registers.

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

packages/halkyon_app/assets/subdivisions/ATTRIBUTION.md

@@ -0,0 +1,12 @@
+# Subdivisions' names
+
+`subdivisions.json` holds the names of states, regions and provinces (ISO 3166-2
+codes, `US-CA`) in English and German, from the Unicode Common Locale Data
+Repository (CLDR, <https://cldr.unicode.org/>), release 48.2 (tag `release-48-2`,
+`common/subdivisions/en.xml` and `de.xml`), converted by the workspace's
+`tool/subdivision_names.py`: English whole, German where it differs, variants left
+out.
+
+CLDR is under the Unicode License v3, whose notice is in `LICENSE-CLDR.txt`,
+verbatim from that release, and in the app's licence list
+(`registerHalkyonAppLicenses`).