Add denial code explainer for CARC and RARC

[aanishs]

Clinician value

Help clinicians and billers understand common claim denial and remittance codes without digging through raw code lists.

Scope

• Add lookup data for CARC and RARC where source terms allow.
• Search by code or phrase.
• Show plain-language explanation, likely next step, and source link.
• Keep output informational and payer-specific verification required.

Acceptance checks

• Lookup works by code.
• Each result links to the official source list.
• Common denial scenarios have clinician-readable next steps.
• The tool does not ask for claim numbers, member IDs, or patient details.