Add superbill sanity checker

[aanishs]

Clinician value

Let clinicians check whether a superbill has the common administrative fields patients and payers expect before they send it.

Scope

• Accept non-PHI checklist-style inputs rather than uploading real superbills in v1.
• Check for provider name, credentials, NPI, taxonomy, tax ID placeholder, service date, CPT code number, diagnosis code placeholder, fee, amount paid, and telehealth/modifier fields when applicable.
• Explain missing items in plain language.

Acceptance checks

• Does not require patient name, DOB, address, member ID, or diagnosis details.
• Avoids redistributing official AMA CPT descriptor text.
• Produces a copyable missing-field checklist.
• Includes a source/caveat section for clinicians.