Add SEC 10-K financial analysis example DAG using LlamaIndex for Common.ai provider (#67671)

Two Dags demonstrating a multi-company financial research pipeline
  using real SEC 10-K filings fetched live from the EDGAR public API:

  - Indexing DAG (weekly): fetches 10-K filings by stock ticker,
    extracts Risk Factors and MD&A sections, builds per-company
    vector indexes via LlamaIndexEmbeddingOperator with DTM fan-out.
  - Analysis DAG (on-demand): analyst submits tickers and a comparison
    question via HITLEntryOperator, LLM decomposes into company-specific
    sub-questions (N decided at runtime), retrieves from per-company
    indexes via DTM, synthesizes a structured report (AnalysisReport
    Pydantic model with UsageLimits), formats for human review, and
    gates on ApprovalOperator.

  Features showcased: Dynamic Task Mapping, structured LLM output,
  UsageLimits, HITL input and approval, live external API integration,
  DAG-level Params.

  Default tickers: AAPL, MSFT, UBER, LYFT, AMZN.