Use encoded style ids for AutoRep representations

[cpignedoli]

What

PR-S1 for surfaces AutoRep support, stacked on the existing split surfaces chain.

This PR adds AutoRep support for the encoded viewer representation IDs introduced in aiidalab-widgets-base PR-R1 (#768) and keeps imported/stored viewer representation arrays intact when structures change.

AutoRep remains surfaces-only because it uses lowdimfinder/surfaces domain logic. The widget writes molecule atoms as ball+stick and non-molecule atoms as spacefill using the same encoded representation naming convention as widgets-base.

Dependencies

• aiidalab-widgets-base PR-R1: Encode structure viewer representation styles aiidalab/aiidalab-widgets-base#768
• aiidalab-widgets-base PR-R2: PR-R2: Load viewer representations from extras aiidalab/aiidalab-widgets-base#769
• aiidalab-widgets-base PR-R3: PR-R3: Persist viewer representations in extras aiidalab/aiidalab-widgets-base#770

Implemented with Codex.

Validation

• Manually tested uploaded encoded XYZ representation arrays.
• Manually tested storing and reloading representation extras through AiiDA nodes.
• Manually tested switching from stored representation-rich structures to plain structures without stale empty rows corrupting the viewer.
• Syntax check:

python -m py_compile surfaces_tools/widgets/auto_representations.py