Redesign database API to match TwoBody.jl

[ohno]

Summary

• align the core database API with TwoBody.jl using DatabaseEntry, put!, db, and dbkeys
• preserve concrete numeric value types instead of storing results as strings
• keep database and bibliography registries private, with validation for duplicate and unknown keys
• retain bib, @get, and @bib for FewBodyDB-specific bibliography access and compatibility
• update tests, README, and Documenter documentation
• remove the no-longer-needed OrderedCollections dependency

Why

The previous implementation exposed mutable registries and relied on macros and slash-separated string values as its main interface. This redesign follows the lookup boundary and typed-entry design used by TwoBody.jl, while retaining FewBodyDB's provenance metadata and existing compatibility wrappers.

Impact

New code can use structured lookups such as:

entry = db(:Bubin2005Jan, Symbol("HD⁺"), :energy, (J = 0, v = 0))
entry.value
bib(entry)

The legacy @get and @bib macros remain available. @get now returns the stored numeric value rather than its string representation.

Validation

• Pkg.test() with Julia 1.11.7: 27/27 tests passed
• Documenter build completed successfully
• git diff --check passed

[codecov]

Codecov Report

❌ Patch coverage is 86.36364% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/FewBodyDB.jl	86.36%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!