fix(contracts): canonical last-price key, dust deposit rejection, bri…

[godamongstmen897]

🚀 Overview

This Pull Request resolves four core smart contract reliability, optimization, security, and integration issues for Junirezz/YieldVault-RWA:

1. Deduplicated Price Storage Keys ([contract] Deduplicate DataKeyExt::Risk variant and dual last-price keys #1525): Consolidated dual last-price keys (Risk(LastPx) and LastOraclePrice) into DataKeyExt::LastOraclePrice with backward-compatible lazy migration and proper cache invalidation on oracle updates.
2. Dust Deposit Rejection ([contract] Reject / test dust deposits minting zero shares #1536): Rejects dust deposits that round down to zero shares with MinDepositNotMet (Error Code 6) and emits diagnostic dep_dust events, preventing locked user funds across deposit, gasless_deposit, and batch entrypoints.
3. Storage Read Caching & Gas Optimization ([contract] Cache repeated storage reads in total_assets / set_strategy #1538): Optimized total_assets and set_strategy by eliminating redundant storage reads and double-writes, verified via gas/footprint benchmark assertions.
4. Bridge Provider Removal & Fallback Routing ([contract] Implement bridge provider removal + fallback routing + endpoint call #1540): Implemented timelocked 3-step bridge provider deregistration (queue, unregister, cancel), active contract invocation via BridgeEndpoint::send, and fallback routing over enabled secondary providers.

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🔑 Linked Issues

• Closes [contract] Deduplicate DataKeyExt::Risk variant and dual last-price keys #1525 ([contract] Deduplicate DataKeyExt::Risk variant and dual last-price keys)
• Closes [contract] Reject / test dust deposits minting zero shares #1536 ([contract] Reject / test dust deposits minting zero shares)
• Closes [contract] Cache repeated storage reads in total_assets / set_strategy #1538 ([contract] Cache repeated storage reads in total_assets / set_strategy)
• Closes [contract] Implement bridge provider removal + fallback routing + endpoint call #1540 ([contract] Implement bridge provider removal + fallback routing + endpoint call)

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🛠️ Summary of Changes

🔑 1. Price Storage Key Consolidation (contracts/vault/src/lib.rs) (#1525)

• Single Canonical Key: Standardized on DataKeyExt::LastOraclePrice as the single canonical storage location for oracle price feeds.
• Lazy State Migration: On read, if only legacy Risk(LastPx) exists, its value is automatically migrated to LastOraclePrice and the legacy key is purged.
• Oracle Change Invalidation: Changing the vault oracle now purges both old and new keys to prevent stale price leaks (fixing a bug where only the un-written legacy key was previously cleared).
• Storage Invariant Tests: Added unit coverage confirming single-key writes, migration execution, and full storage clearing on oracle mutations.

🛡️ 2. Zero-Share Dust Deposit Rejection (contracts/vault/src/lib.rs, contracts/share-price-math/src/rounding.rs) (#1536)

• Zero-Share Guard: Rejects asset deposits that result in zero minted shares (e.g. 1 asset into 1,000 shares / 1,000,000 asset vault state).
• Soroban Error Budgeting: Reused MinDepositNotMet (Code 6) to remain strictly within Soroban's 50-variant VaultError enum ceiling without breaking existing error mappings.
• Diagnostic & Batch Events: Emits a dep_dust diagnostic event detailing input amount and vault totals. In batch entries where execution does not revert, events persist for off-chain indexing.
• Boundary Tests: Verified zero-mint boundaries (999 assets fail, 1,000 assets mint 1 share), batch behaviors, and rounding logic.

⚡ 3. Storage Read/Write Optimization (contracts/vault/src/lib.rs) (#1538)

• In-Memory Caching: Refactored total_assets to read token configuration once and cached intermediate storage reads across single calls. set_strategy now caches ledger timestamps.
• Write Elimination: Replaced duplicate key writes with a single atomic price write per invocation.
• Footprint Benchmark Test: Added footprint comparison assertions demonstrating lower CPU and memory footprint consumption for the updated read/write patterns.

🌉 4. Bridge Provider Removal & Fallback Routing (contracts/bridge-compat/src/lib.rs) (#1540)

• Timelocked Unregister Flow: Implemented admin-governed provider removal via queue_unregister_provider, a 24-hour timelock delay, and unregister_provider. Supported cancellation via cancel_unregister_provider. Automatically clears default provider assignments if the default provider is removed.
• Endpoint Contract Calls: Updated transfer_out to invoke BridgeEndpoint::send on the target provider contract.
• Fallback Execution: If the primary provider call fails, transfer_out iterates through remaining enabled providers supporting the destination chain in ID order. Reverts with NoFallbackAvailable if all providers fail, ensuring sender tokens are preserved.
• Mock Provider Test Suite: Added 16 unit tests utilizing a mock provider contract, and updated existing test fixtures to handle hashed provider identifiers.

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📁 Files Touched

File / Path	Change Summary
contracts/vault/src/lib.rs	Storage key deduplication, migration logic, dust deposit guards, and storage read caching.
contracts/share-price-math/src/rounding.rs	Added unit tests for zero-share rounding edge cases and fixed import placements.
contracts/bridge-compat/src/lib.rs	Timelocked provider removal, endpoint invocations, fallback routing, and mock provider tests.
contracts/vault/src/fuzz_math.rs & tests/	Fixed minor import errors in timelock.rs, whitelist.rs, and strategy_registration.rs to allow test compilation.

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🧪 Verification Logs

• bridge-compat: 16 / 16 tests passed.
• share-price-math: 13 / 13 tests passed.
• vault: All 23 new and modified tests passed cleanly (including gas footprint comparison, migration, dust rejection, and single-key invariant tests).
• Compilation: Repaired top-level test import errors across vault helper modules. Pre-existing test failures on main (auth mocking and strategy setup failures) remain unchanged.

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