Partners app: list-form reads and shared-module dedup (#24784)

Part 2 of 5, stack root: `rashad/partners-website-brief-modal`. This
slice is the root of the four partners-app slices and targets `main`
directly.

Mechanical cleanup under
`packages/twenty-apps/internal/twenty-partners`, no behaviour change
beyond error handling.

**List-form reads.** The single-record GraphQL read (`partner { ... }`)
throws `Record not found` for an unknown id, which turned a missing row
into a failed trigger. Every such read now uses the list form
(`partners(filter, first: 1) { edges { node } }`) and returns `null`
instead. Callers, their tests and the new absent-row cases follow.

**Shared-module dedup.** `findPartnerByMember`, `getCompanyPartnerUser`
and the front-component `COLORS`/`FONT` palette each existed in two or
three copies. One copy each now lives under `src/modules/shared/`; the
duplicates are deleted and the importers repointed.

**Also here.** `buildApplicationName` extracted with its own test, the
`partner.role` / `configure-partner-rls.ts` cleanups, and the app-level
`.gitignore` entries.

Note: `src/constants/universal-identifiers.ts` arrives whole, including
the two logic-function UUIDs used by parts 3 and 5. They are inert data
lines until those slices land.

`yarn test:unit`: 245 passing, 35 files.


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