fix: resolve LNURL-pay usernames case-insensitively (#3058)

[protivon]

Description

Fixes #3058. Paying a mixed-case Lightning address such as SwapMarket@stacker.news returned "user @SwapMarket does not exist", while the lowercase form worked.

Both LNURL-pay endpoints resolved the recipient with:

models.user.findUnique({ where: { name: username } })

The users.name column is Citext, so equality in Postgres is case-insensitive — but Prisma's findUnique on the unique key does not reliably fold case for the bound parameter here, so a mixed-case username from the URL missed the row. The codebase already compensates for this elsewhere by comparing names with .toUpperCase() (see api/resolvers/user.js).

This PR makes the two LNURL-pay lookups explicitly case-insensitive:

models.user.findFirst({ where: { name: { equals: username, mode: 'insensitive' } } })

in pages/api/lnurlp/[username]/index.js (the LNURL-pay metadata response) and pages/api/lnurlp/[username]/pay.js (the invoice/callback). Any casing of an existing username now resolves to the same account.

Screenshots

N/A — server-side payment-resolution fix, no UI change.

Additional Context

name is both @unique and Citext, so a case-insensitive match returns at most one row; findFirst is therefore equivalent to findUnique for valid data while tolerating casing. This cannot create users or change who an address maps to — it only lets an already-existing recipient be found regardless of the sender's casing.

Checklist

Are your changes backward compatible? Please answer below:

Yes. Lowercase addresses behave exactly as before; only previously-failing mixed-case lookups now succeed. No schema, GraphQL, or API-shape changes.

On a scale of 1-10 how well and how have you QA'd this change and any features it might affect? Please answer below:

7/10. Verified the root cause by reading the schema (name … @db.Citext, line 19 of prisma/schema.prisma) and confirming both LNURL-pay routes used the case-sensitive findUnique. Confirmed mode: 'insensitive' is supported on the project's Prisma 5.20 findFirst. Both changed files pass node --check. I did not spin up the full stack to send a live mixed-case LNURL payment, so an end-to-end test against a running node would be the remaining QA step.

For frontend changes: Tested on mobile, light and dark mode? Please answer below:

N/A — no frontend changes.