refactor: replace in-memory cache with pg-backed repository - #667

apps/backend/src/wallet-sdk/wallet-sdk.service.ts:112

• Important: ensureProvidersLoaded can still trigger a multi-pod thundering herd on cold start. If the DB is empty, every pod will see countByNetwork() === 0 and call loadProviders() (chain RPC) concurrently, which can reintroduce the rate-limit bursts this PR is trying to eliminate. Consider adding a Postgres-backed distributed lock (e.g. advisory lock per network) around the "count==0 → load" path and re-checking the count after acquiring the lock.
  apps/backend/src/piece-cleanup/piece-cleanup.service.spec.ts:457
• This assertion expects a number (9), but deletePiece(..., providerId) is typed as bigint | undefined and should receive 9n from the repository. Keeping the assertion as a number can let a regression slip through if providerId ever gets coerced incorrectly.

      for (const call of deletePieceSpy.mock.calls) {
        expect(call[5]).toBe(9);
      }

apps/backend/src/providers/repositories/storage-provider.repository.ts:116

• Blocker: findByAddressesCaseInsensitive lowercases the DB column (LOWER(address)), but it passes the input addresses array through unchanged. If any input address is mixed-case, the IN (...) comparison will not match and stale-provider cleanup will silently miss rows.

      where: {
        network,
        address: Raw((alias) => `LOWER(${alias}) IN (:...addresses)`, { addresses }),
      },

apps/backend/src/providers/repositories/storage-provider.repository.ts:30

• Blocker: findByAddress performs a case-sensitive match on address, which can miss rows when callers provide checksummed/mixed-case addresses (common for EVM-style addresses). This can cause providers to appear “not found” even though they exist in Postgres, leading to skipped jobs or failed checks.

  async findByAddress(address: string, network: Network): Promise<PDPProviderEx | undefined> {
    const row = await this.repo.findOne({ where: { address, network } });
    return row ? this.hydrateProvider(row) : undefined;

apps/backend/src/piece-cleanup/piece-cleanup.service.spec.ts:89

• The repository mock returns id: 9 (number), but production provider ids are bigint (PDPProviderEx.id). Using a number here can mask type/serialization issues and makes the new providerId-passing optimization less faithful to runtime behavior.

This issue also appears on line 455 of the same file.

  function createStorageProviderRepositoryMock() {
    return {
      findByAddress: vi.fn().mockResolvedValue({ id: 9, name: "Test SP" }),
    };