Support widget Multi-language support

Feature request

Support widget: no way to configure/localize language

Description:

Currently, the Support widget (posthog.com/docs/support/widget) has no built-in way to set or change its display language. Reviewing the widget configuration docs, the only customizable text fields are:

• Greeting message (free text)
• Form title / Form description (free text, shown on the identification form)

While these let teams manually translate a handful of strings, other UI elements appear to be hardcoded in English, including:

• "Recover your tickets" link and flow
• "Before we start..." default form copy (if not overridden)
• System/status messages within the chat interface
• Any other built-in labels not exposed as configurable settings

Expected behavior

Some way to set the widget's display language, either via:

1. A language / locale option in the PostHog init config (e.g. posthog.init(token, { conversations_locale: 'fr' })), or
2. Automatic detection based on the visitor's browser locale, with a manual override option, or
3. Full translation support so all built-in strings (not just the free-text fields) can be localized

Why this matters

Teams supporting non-English-speaking users currently have no clean way to present a fully localized support experience — only the few free-text fields can be translated, while the rest of the widget's UI remains in English.

Additional context

• Docs reviewed: https://posthog.com/docs/support/widget
• Support product is currently in Beta

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

Start with the support widget configuration documentation at posthog.com/docs/support/widget and compare the currently exposed text fields with the built-in English UI described in the issue. Done means the widget has a defined way to select or detect a locale and its built-in labels, status messages, recovery flow, and default form copy are localized.