fix(customer-modal): replace Mantine Autocomplete with native input (React 19 ref warning)

[giladresisi]

Why this change (the problem)

Opening the Customer modal — e.g. when adding a channel into a new group — throws a React 19 console error:

Accessing element.ref was removed in React 19. ref is now a regular prop. It will be removed from the JSX Element type in a future release.

Origin: src/components/launches/customer.modal.tsx rendering @mantine/core's <Autocomplete>. The real cause is @mantine/core@5.10.5 (Mantine v5, built for React 17/18) running under React 19.2.4 — the library internally accesses the now-removed element.ref. It's a console error (not a hard crash), but it's noisy and user-visible in dev.

The fix

Replace the single <Autocomplete> with a native <input> + <datalist>, styled to match the app's existing inputs. Preserves the important behaviors:

• Free-text entry (needed to create a new customer/group by typing a new name)
• Existing-name suggestions from GET /integrations/customers

Save/remove logic and the PUT /integrations/:id/customer-name endpoint are untouched.

Why this solution (and not upgrading Mantine)

The alternative was to bump @mantine/core to a React 19-compatible major (v8). That was clearly unfavorable:

• Mantine is used in only two files in the frontend — it's a vestigial dependency.
• Project convention is to prefer native components over npm UI libraries.
• A v5 → v8 bump is a large breaking change (both files would need reworking) carrying far more risk than removing one component.

So we removed the component instead of dragging in a major dependency upgrade.

Scope & risk

• Changed one file (customer.modal.tsx). @mantine/core stays in package.json (still used by layout/language.component.tsx), so no dependency/build impact elsewhere.
• Main trade-off: the suggestion dropdown is now browser-native (styling differs across Chrome/Safari/Firefox) rather than Mantine-themed.
• Note: the same React 19 element.ref warning can still originate from language.component.tsx (also Mantine v5); fully removing Mantine is out of scope here.

Testing

Verified manually: the console error is gone; typing shows existing customer suggestions; typing a new name + Save creates/assigns the group and persists; opening for an already-assigned channel pre-fills the name and "Remove from customer" works; empty save is a no-op.

🤖 Generated with Claude Code

[postiz-contribution]

Contribution-checker quality warning
Heuristic score: 7/100 (low). This is a non-blocking warning surfaced by the project's quality settings.

Heuristics that flagged:

• Excessive inline code references: 17 inline refs (>3)
• PR doesn't use the repo's PR template: 5 required checkbox items missing (max 1, match ≥80%)
• Body adds too many extra headers beyond the template: 5 extra headers (>1)
• AI watermark phrase: Matched: "Generated with Claude Code"
• Commit message too long: Longest: 1191 chars

If this is a genuine contribution, please add detail to your PR description and tighten the diff scope before reviewers look at it.

[postiz-agent]

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