Add UAE (VARA) as 5th jurisdiction

[DROOdotFOO]

Summary

Adds UAE (VARA) as a 5th jurisdiction across the Noir circuits and Solidity library so the reference implementation matches the policy described in the whitepaper's VARA strategy (whitepaper Section 8.4).

Why

VARA's January 2026 anti-anonymity ruling carves out assets with "mitigating technologies" for traceability. ERC-8262 is that technology, and UAE is named in the whitepaper as the first regulatory target. Without UAE in the Solidity `JurisdictionConfig` and the matching Noir circuit constant, UAE-originating attestations could not route through the on-chain validation pipeline.

Policy

Parameter	Value	Rationale
High-risk threshold	7100 bps (71%)	Matches EU/UK
`requireSignedSignals`	`true`	Strict, same as US BSA / Singapore MAS
`minMultiProviderThreshold`	2	Strict, same as US BSA / Singapore MAS

Changes

• `circuits/shared/src/constants.nr` — `JURISDICTION_UAE = 4`
• `circuits/shared/src/risk.nr` — `get_high_threshold` covers UAE; cross-validation test asserts the threshold
• `src/libraries/JurisdictionConfig.sol` — UAE constant + `getThresholds`, `validateJurisdiction`, `requireSignedSignals`, `minMultiProviderThreshold` all updated
• `test/ThresholdCrossValidation.t.sol` — `NOIR_UAE_THRESHOLD` constant, `test_uae_threshold_matches_noir`, exhaustive loop now iterates `0..5`
• `test/LibraryFuzz.t.sol` — fuzz bounds widened to include UAE
• `test/ERC8262Oracle.t.sol`, `test/Invariant.t.sol` — comments updated to reflect strict-mode set now being US/SG/UAE

Companion PRs

• `Add ERC: Zero-Knowledge Compliance Oracle ethereum/ERCs#1747` — adds UAE row to the ERC's Jurisdiction Configuration table
• `xochi-fi/xochi` (forthcoming) — adds UAE mentions to whitepaper Sections 2 & 9 and to the multi-signed description in the appendix

Test plan

• `forge build` succeeds
• `forge test --match-contract "ThresholdCrossValidation|LibraryFuzz"` — 12 tests pass
• `forge test` (full suite) — please run before merge
• `nargo test --workspace` in `circuits/` — please run before merge (`nargo` not in CI here)