Add lazy option to QuantumOpticsRepr

[DennisWayo]

This PR adds a small option to QuantumOpticsRepr so downstream packages can ask for a lazy QuantumOptics representation without changing the current default behavior.

The main change is that QuantumOpticsRepr now carries a lazy::Bool field:

julia> QuantumOpticsRepr()
QuantumOpticsRepr(2, false)

julia> QuantumOpticsRepr(lazy=true)
QuantumOpticsRepr(2, true)

julia> QuantumOpticsRepr(cutoff=4, lazy=true)
QuantumOpticsRepr(4, true)

The default remains eager conversion (lazy=false), and the existing positional cutoff form is preserved:

julia> QuantumOpticsRepr(4)
QuantumOpticsRepr(4, false)

This PR is intentionally only the interface piece. The actual lazy conversion behavior is implemented in the companion QuantumSymbolics PR:

QuantumSavory/QuantumSymbolics.jl#201

Why this is useful:

• keeps the public representation choice in QuantumInterface.jl, where QuantumOpticsRepr is defined;
• lets existing callers keep getting the same eager conversion behavior;
• gives packages like QuantumSymbolics.jl a clean way to opt into LazySum, LazyProduct, and LazyTensor construction.

Tests added:

• default QuantumOpticsRepr() keeps cutoff == 2 and lazy == false;
• QuantumOpticsRepr(4) still works as before;
• QuantumOpticsRepr(lazy=true) and QuantumOpticsRepr(cutoff=4, lazy=true) store the requested values.

Local test command:

julia --project=. -e 'using Pkg; Pkg.test()'

OSS Contributions
PennyLaneAI/pennylane#9566
PennyLaneAI/pennylane#9604
https://www.linkedin.com/posts/activity-7443523751436091392-depM?utm_source=share&utm_medium=member_desktop&rcm=ACoAABfS9T0BJJPP6KT13py3QtCdMEGtOb3Q3PE

AI Use Disclosure: Code syntax was assisted by Codex model. All handwritten code and accompanying text were thoroughly reviewed and verified by me prior to submission. I retain full responsibility for the final contribution.