Add Right‑Click Query for Matching Documents in DataGridView

[rffrasca]

Is your feature request related to a problem? Please describe.
Users often need to quickly locate related documents. Currently, this requires performing a search using the Find dialog. A contextual action would streamline this workflow and reduce repetitive input.

Describe the solution you'd like
Introduce a right‑click context menu option on a document row in the main DataGridView that performs a query for all documents sharing the selected document’s Author, Subject, Category, and Tax Year fields.

Proposed Behavior
When the user right‑clicks a document row:

1. A context menu appears with a new item: “Find Matching Documents…”
2. Selecting this option triggers a query that filters the document list to all entries where:
   • Author matches the selected document’s Author
   • Subject matches the selected document’s Subject
   • Category matches the selected document’s Category
   • Tax Year matches the selected document’s Tax Year
3. The main grid updates to display the filtered results.