feat(data-warehouse): add 30 warehouse sources to the self-driving inbox

[Gilbert09]

Problem

The Self-driving Inbox let users connect only 5 warehouse sources (GitHub, Linear, Jira,
Zendesk, pganalyze) even though PostHog supports ~500. The backend signals scout now emits
from 30 more sources, but there was no way to toggle or connect them in the app.

Changes

Wires 30 new warehouse sources into the Self-driving sources UI — support desks
(Freshdesk, Freshservice, Front, Gorgias, Kustomer, Dixa, Plain), issue trackers (GitLab,
Gitea, Shortcut), error tracking (Sentry, Rollbar, Bugsnag, Honeybadger, Raygun), security
scanners (Snyk, SonarQube, Semgrep, Rapid7 InsightVM), and product feedback / reviews
(Featurebase, Frill, Aha, UserVoice, Productboard, Canny, AskNicely, Retently, Appfigures,
AppFollow, Judge.me).

The inbox source wiring was hand-coded per source across ~8 files, which doesn't scale. This
PR refactors it to be data-driven:

• A single EXTERNAL_INBOX_SOURCES registry in packages/shared/src/inbox-types.ts is the
  source of truth (product, label, description, DWH type, tables, record kind, setup flow).
• The toggle grid, DataSourceSetup switch, source-type map, DWH connection map, icons, and
  filter options all derive from it. Adding a source is now one registry entry.
• The "External connections" column renders from the registry (with a memoized per-source
  card) instead of hand-coded <SignalSourceToggleCard>s.
• Credential sources route through the existing generic DynamicSourceSetup — no per-source
  form code. The legacy GitHub repo-picker / Zendesk / pganalyze flows are unchanged.
• Adds two record kinds (feedback, review), expands the SignalSourceConfig +
  analytics-event source_product unions, and forces full-refresh sync for issue-like records
  (issues, findings, feedback, reviews) while tickets stay append-only.

The core SignalSourceService mirror and the mobile SourceProduct type were kept consistent.

Deploy ordering: the backend PostHog PR (PostHog/posthog#72378) — new SignalSourceProduct
enum values + migration — must ship first, since the toggle calls createSignalSourceConfig
with these source_product values and the model rejects unknown ones (400).

How did you test this?

Automated (run by me):

• turbo typecheck for @posthog/ui, @posthog/core, @posthog/shared, @posthog/api-client,
  and @posthog/mobile — all pass.
• pnpm --filter @posthog/shared build — the published type builds.
• biome check on all changed files — clean.

Not done: no manual click-through of the connect flow in a running app (the generic
DynamicSourceSetup path is already exercised by the shipped Linear/Jira sources this reuses).

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[github-actions]

React Doctor found 2 issues in 1 file · 2 warnings.

2 warnings

src/features/inbox/components/SignalSourceToggles.tsx

• ⚠️ src/features/inbox/components/SignalSourceToggles.tsx:169 Multiple components in one file no-multi-comp
• ⚠️ src/features/inbox/components/SignalSourceToggles.tsx:198 Inline prop defeats memo() no-inline-prop-on-memo-component

_{Reviewed by React Doctor for commit 313ed86.}