feat: support HDFC SmartHub Vyapar notifications

[Phloraxx]

Summary

• trust the official HDFC SmartHub Vyapar Android package (com.hdfc.smarthub) as a generic notification source
• cover HDFC incoming-payment parsing, amount extraction, payer identity, and notification timestamps
• label HDFC evidence clearly in the PayGate operator UI

Verification

• npm run typecheck:v4
• npm run build:v4
• full Go formatting, tests, race tests, vet, static analysis, vulnerability scan, and container build run in CI

The Android relay remains unchanged because its prefilter is deliberately source-agnostic and already forwards non-zero-paise notification evidence.