feat: session key support and Safe multisig tooling

[rvagg]

Add session key authentication for delegated signing from a Safe multisig wallet. When SESSION_KEY_PRIVATE_KEY is set, DealBot uses scoped session key permissions instead of direct wallet signing.

• Add SESSION_KEY_PRIVATE_KEY env var (mutually exclusive with WALLET_PRIVATE_KEY)
• Session key mode in both deal service and wallet SDK Synapse creation
• Read-only account readiness check via synapse-core getUploadCosts in session key mode
• Scripts: create-session-key-safe.mjs (session key registration calldata), fund-safe.mjs (USDFC deposit + FWSS operator approval calldata)
• Runbook: docs/runbooks/wallet-and-session-keys.md
• @filoz/synapse-core added as dev dependency for scripts and readiness check

[Copilot]

Pull request overview

Adds support for operating DealBot using a Safe multisig as the root wallet while delegating day-to-day signing to a scoped, expiring session key. This includes backend wiring for session key auth, operational runbooks, and helper scripts for Safe transaction calldata.

Changes:

• Add SESSION_KEY_PRIVATE_KEY configuration and session-key-mode Synapse initialization in backend services.
• Add readiness/allowance handling for session-key mode plus related test updates.
• Add operational runbook + Safe calldata generation scripts for session key registration and funding/approvals.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
apps/backend/src/config/app.config.ts	Adds SESSION_KEY_PRIVATE_KEY to config + updates validation/loading logic.
apps/backend/src/deal/deal.service.ts	Creates Synapse instance using session key when configured (async init).
apps/backend/src/wallet-sdk/wallet-sdk.service.ts	Initializes Synapse in session-key mode and changes allowance behavior accordingly.
apps/backend/src/wallet-sdk/wallet-sdk.service.spec.ts	Adds config-validation tests and basic session/direct allowance-path tests.
apps/backend/scripts/create-session-key-safe.mjs	Generates Safe calldata for registering a session key on-chain.
apps/backend/scripts/fund-safe.mjs	Generates Safe batch calldata for USDFC deposit and FWSS operator approvals.
docs/runbooks/wallet-and-session-keys.md	New runbook documenting Safe + session key lifecycle and funding flows.
docs/environment-variables.md	Documents SESSION_KEY_PRIVATE_KEY and updates wallet key guidance.
docs/production-operations.md	Links to the new wallet/session key runbook.
apps/backend/package.json	Adds @filoz/synapse-core (currently as a dev dependency).
pnpm-lock.yaml	Lockfile update for @filoz/synapse-core.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (1)

apps/backend/src/config/app.config.ts:114

• IBlockchainConfig.walletPrivateKey is typed as required, but config validation now makes WALLET_PRIVATE_KEY optional (session key mode). This can leak undefined/"" into runtime code paths that still assume a real private key. Suggest making walletPrivateKey optional in the interface and only constructing an account when it’s actually present/selected by validation.

export interface IBlockchainConfig {
  network: Network;
  rpcUrl?: string;
  sessionKeyPrivateKey?: `0x${string}`;
  walletAddress: string;
  walletPrivateKey: `0x${string}`;
  checkDatasetCreationFees: boolean;
  useOnlyApprovedProviders: boolean;

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