Add official Luxembourg source objects for inheritance declaration

[TommiLindfors]

Scope

Add structured Source objects for Luxembourg's inheritance-declaration process. Cover notarial procedures, the Administration de l'enregistrement, succession tax references, and renunciation procedures.

Source links

• https://guichet.public.lu/en/citoyens/famille/deces/heritage/declaration-succession.html
• https://guichet.public.lu/fr/citoyens/famille/deces/heritage/declaration-succession.html

Acceptance criteria

• Source objects added to data/sources/lu/
• Source URL included
• Access date included
• Language included
• Jurisdiction set to lu
• Validation passes
• Review status assigned (discovered or structured-from-source)

Trust level

maintainer-only