feat(settings): show Slack workspace connection status

[dmarticus]

Problem

The Slack settings panel only showed a "Manage in PostHog" button — there was no way to see at a glance whether a Slack workspace was already connected to the project, or which workspace it was.

Changes

• Add slackIntegrations / hasSlackIntegration selectors to integrationStore (mirrors the existing GitHub selectors).
• SlackSettings now renders connection state above the manage button:
  • Loading spinner while integrations fetch.
  • One row per connected workspace (Slack logo, workspace name, relative "Created…" timestamp).
  • Empty-state row when nothing is connected.
• Renamed the manage button local to manageButton / manageButtonWithTooltip for clarity.

Before

(no indication if we've connected or not)

After

(with connection)

(with no connection)

How did you test this?

• pnpm typecheck (ran via lint-staged on commit).
• Manually opened Settings → Slack and verified: empty state when not connected, populated row when a workspace is connected, and that the tooltip-disabled state still shows when not signed in to a project.

Publish to changelog?

no

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
apps/code/src/renderer/features/settings/components/sections/SlackSettings.tsx:93-97
The `typeof ... === "number"` branch in `createdAt` accepts a raw number, but `formatRelativeTimeLong` treats any number as Unix **milliseconds** — `new Date(seconds)` would produce a date in early 1970. PostHog APIs consistently return ISO strings for `created_at`, so this branch is probably dead code. If it can ever be reached, the caller needs to convert seconds → ms first. Narrowing the guard to `string` only matches the actual API contract and avoids a silent wrong-date bug if a numeric value ever surfaces.

```suggestion
  const createdAt =
    typeof integration.created_at === "string"
      ? integration.created_at
      : null;
```

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