Add more language parsers (Rust, Java, Ruby, Shell, SQL)

[jonyoder]

Potential languages to add based on demand:

• Rust — tree-sitter grammar available in smacker/go-tree-sitter
• Java — tree-sitter grammar available
• Ruby — tree-sitter grammar available
• Shell/Bash — regex-based, extract functions
• SQL — regex-based, extract stored procedures/views

Each language requires ~200-300 lines: a parser file + language detection in generate.go and parse.go.

Priority should be driven by user demand.