Update mina-rust to use const generic FULL_ROUNDS in poseidon sponge types

[dannywillems]

Summary

proof-systems PR #3386 changed ArithmeticSpongeParams and related sponge types to use const generics instead of vectors:

• ArithmeticSpongeParams<F> → ArithmeticSpongeParams<F, FULL_ROUNDS>
• ArithmeticSponge<F, SC> → ArithmeticSponge<F, SC, FULL_ROUNDS>
• DefaultFqSponge<P, SC> → DefaultFqSponge<P, SC, FULL_ROUNDS>
• DefaultFrSponge<Fr, SC> → DefaultFrSponge<Fr, SC, FULL_ROUNDS>
• FqSponge trait now has const FULL_ROUNDS: usize parameter

Benefits

• Better memory layout (stack/contiguous instead of scattered heap allocations)
• Fewer dynamic allocations
• Small but consistent performance improvement

Affected crates

• ledger (proofs, verification, field operations)
• snark

Tasks

• Update proof-systems dependency to 0.3.0
• Update all usages of DefaultFqSponge and DefaultFrSponge with appropriate FULL_ROUNDS values
• Update FqSponge trait bounds
• Verify tests pass

Related

• This must be done at the same time as Update mina-rust to use the tag 0.3.0 of proof-systems #1972.
• Blocked by: proof-systems release 0.3.0
• Part of: Release 0.3.0 of proof-systems #1970