refactor: extract shared fetchAndStoreSubmission helper; fix invalid empty date in BootstrapSubmissionsTask

[Copilot]

BootstrapSubmissionsTask passed date: "" per CIK, which fails TypeOptionalSecDate format validation (requires YYYY-MM-DD when present). Additionally, fetchAndStoreSubmission was duplicated across BootstrapSubmissionsTask and UpdateAllSubmissionsTask, risking drift in error handling and concurrency behavior.

Changes

• New src/task/submissions/fetchAndStoreSubmission.ts — extracts the shared pipeline helper with date?: string (optional), consolidating fetch+store+error-recording logic in one place
• BootstrapSubmissionsTask — imports shared helper; drops date from wf.run() inputs entirely since no date is available at bootstrap time
• UpdateAllSubmissionsTask — imports shared helper; removes local duplicate and unused pipe import

// Before: invalid empty string injected per CIK
await wf.run({
  cik: unprocessedCiks,
  date: unprocessedCiks.map(() => ""),  // fails sec-date format validation
});

// After: date omitted; shared helper accepts date?: string
await wf.run({
  cik: unprocessedCiks,
});

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