feat: enable Rich Text as a creatable field type (#18634)

## Summary

- Removes `RICH_TEXT` from the excluded/hidden field types in the
settings UI so users can create rich text fields on any object (not just
Note/Task)
- Creates a generic `RichTextFieldEditor` component that uses standard
`useUpdateOneRecord` for persistence, decoupled from the
Note/Task-specific `ActivityRichTextEditor`
- Updates the inline `RichTextFieldInput` and side panel to route to the
appropriate editor based on object type (activity editor for Note/Task,
generic editor for everything else)

## Details

### Tier 1 — Settings UI unlock
- Removed `RICH_TEXT` from `excludedFieldTypes` in
`SettingsObjectNewFieldSelect.tsx`
- Removed `RICH_TEXT` from `SettingsExcludedFieldType` type union
- Added `RICH_TEXT` to `previewableTypes` in
`SettingsDataModelFieldSettingsFormCard`

### Tier 2 — Generic inline editing
- New `RichTextFieldEditor` — a generic BlockNote editor that works for
any object using `useUpdateOneRecord` (no activity-specific coupling)
- `RichTextFieldInput` now branches: `ActivityRichTextEditor` for
Note/Task, `RichTextFieldEditor` for all other objects
- Generalized side panel state (`viewableRichTextComponentState`) from
`activityId`/`activityObjectNameSingular` to
`recordId`/`objectNameSingular`/`fieldName`
- `useOpenRichTextInSidePanel` now accepts an optional `fieldName`
parameter

### Tier 3 — Verification
- Search: only `markdown` subfield is indexed (correct behavior)
- Filters: `RichTextFilter` GraphQL input type already exists
- Import/export: `markdown` subfield is already marked `isImportable:
true`

packages/twenty-front/src/modules/side-panel/hooks/useOpenRichTextInSidePanel.ts

@@ -12,10 +12,11 @@ export const useOpenRichTextInSidePanel = () => {
   const store = useStore();
 
   const openRichTextInSidePanel = useCallback(
-    (activityId: string, activityObjectNameSingular: string) => {
+    (recordId: string, objectNameSingular: string, fieldName?: string) => {
       store.set(viewableRichTextComponentState.atom, {
-        activityId,
-        activityObjectNameSingular,
+        recordId,
+        objectNameSingular,
+        fieldName: fieldName ?? 'bodyV2',
       });
 
       openSidePanelMenu();