docs: declare where the data comes from, and under what terms

The module's own Apache-2.0 licence covers its code and says nothing
about the material it fetches. STORE.yaml now carries a data_source
block (publisher, url, terms, required attribution, and bundled:
false), and MODULE.md/MODULE.de.md explain it in both languages,
including the sentence that the retrieved text does not replace the
official version.

Enforced platform-side by data_source_gap in chain_hub::store_index;
the four rules are written up in docs/architecture/store-format.md of
the platform repo.

Signed-off-by: flemming-it <sf@flemming.it>

MODULE.md

@@ -41,6 +41,21 @@ Outputs: `formex` (bytes, `application/xml`) and `meta` (JSON with
 `celex`, `language`, `url`, `source_sha256`, `byte_len`, and
 `consolidation_date` for consolidated CELEX numbers).
 
+## Data source
+
+EUR-Lex / CELLAR (Publications Office of the EU)
+
+Attribution: `Quelle: EUR-Lex, © Europäische Union, 1998-2026`
+
+Reuse of EUR-Lex documents is permitted under Commission Decision
+2011/833/EU, commercially and non-commercially; editorial content is
+CC BY 4.0. The condition is the attribution. Individual documents may
+carry different terms (the International Accounting Standards, for one);
+where they do, the Official Journal says so at the document.
+
+**The returned text does not replace the official publication in the
+Official Journal.**
+
 ## License
 
 Apache-2.0 — a Ch∆In platform module (Flemming.AI).