fix(portfolio): filter soft-deleted vaults from user portfolio aggregation (#1438)

[Awosdot]

What changed

• Updated vaultPosition queries in backend/src/routes/portfolio.ts to apply where: { vault: { deletedAt: null } } by default[cite: 11].
• Added support for includeDeleted?: boolean query parameter (defaulting to false) to allow optional inclusion of soft-deleted vaults[cite: 11].
• Updated OpenAPI spec documentation and generated schema snapshots to reflect the new includeDeleted parameter on GET /users/:id/portfolio[cite: 11].
• Added integration tests validating default exclusion of soft-deleted vaults and explicit inclusion when ?includeDeleted=true is set[cite: 11].

Why

Soft-deleted vaults resulting from deprecated strategies were previously included in GET /users/:id/portfolio calculations, showing inflated TVL/PNL gains and causing total value mismatches against GET /vaults[cite: 11].

How tested

• Executed integration tests covering vault creation, soft-deletion, and default vs. includeDeleted=true response validation[cite: 11].
• Verified existing portfolio happy-path test suite passes cleanly[cite: 11].

Closes

Closes #1438