Add professional financial statement formatter to finquick #76

Problem

Financial data from GnuCash SQLite databases often needs to be presented in a professional, readable format with proper currency symbols, thousands separators, and column alignment. Currently, raw SQL output is difficult to read and share.

Proposed Solution

Add a new package packages/format-financial/ with a Python script that formats financial data tables with:

Key Features

• Currency formatting: Automatic $ symbols and thousands separators ($1,234.56)
• Perfect column alignment: Dynamic width calculation for clean tables
• Dual output modes: Both plain text (terminal-friendly) and markdown table formats
• Decimal precision: Uses Python's Decimal class to avoid floating-point errors
• Testable design: I/O separated from formatting logic with comprehensive doctests

Usage Examples

# Plain text output (also valid markdown)
python3 format_financial.py database.sqlite view_name

# Pure markdown output  
python3 format_financial.py database.sqlite view_name --markdown

Sample Output

| as_of_date |      assets | liabilities |   net_worth | retained_earnings |      equity |    eq |
| ---------: | ----------: | ----------: | ----------: | ----------------: | ----------: | ----: |
| 2024-12-31 | $796,380.82 |       $0.00 | $796,380.82 |        $25,222.54 | $771,158.28 | $0.00 |
| 2025-06-30 | $811,111.21 |       $0.00 | $811,111.21 |        $36,153.82 | $774,957.39 | $0.00 |

Technical Implementation

• Object capability discipline: SQLite connections and stdout injected for testability
  • cf. OCap style guide, lint tool for .py awesome-ocap#69
• doctests: any code that doesn't work the first time gets fixed with red/green TDD using doctest

Benefits

• Professional financial reports suitable for sharing
• Works with any SQLite view/table containing financial data
• Eliminates manual formatting of GnuCash query results
• Reusable across different finquick workflows
• Well-tested and maintainable code