CodeGen: base-view label joins are INNER for NOT NULL FKs, so a display label can empty the view

## Summary

CodeGen emits a base-view "label" join as `INNER JOIN` whenever the foreign-key column is NOT NULL. A join that exists purely to fetch a display name can therefore **delete every row of the view**.

## Cause

`packages/CodeGenLib/src/Database/sql_codegen.ts:2095`:

```ts
`${ef.AllowsNull ? 'LEFT OUTER' : 'INNER'} JOIN ... ON x. = alias.`
```

The join's only purpose is to add `_Virtual`, the related entity's name field. Its cardinality is a display concern, but its join type decides whether rows survive.

## Impact

Observed in production: a wrong `RelatedEntityFieldName` on a NOT NULL column (from a generator bug, companion issue) made the predicate match nothing, so a view backed by a 67,389-row table returned **0 rows**. The same defect on a nullable column would have produced NULL labels and no data loss.

Two properties make this hard to notice:

- The failure is silent. No error, no warning, and consumers see an empty result set as "no data".
- Any aggregate over the view returns 0 rather than failing, so it can be presented as a real answer.

There is currently no config to force LEFT joins; the only escapes are per-field (`IncludeRelatedEntityNameFieldInBaseView = 0`, `RelatedEntityJoinFields.mode = 'disable'`, or removing the related entity's name field).

## Suggested fix

Emit `LEFT OUTER JOIN` for label joins unconditionally. A missing label should render as NULL, never remove a row. If INNER is wanted for genuine referential-integrity cases, make it opt-in per field rather than derived from `AllowsNull`.

At minimum, restrict INNER to cases where the target is the related entity's primary key **and** the FK is enforced by a real constraint.

Start at packages/CodeGenLib/src/Database/sql_codegen.ts:2095 and trace how base-view label joins are generated from foreign-key metadata. Verify the generated view preserves source rows when a related display label is missing or mismatched, while still producing the label when available; add or run regression coverage for both nullable and NOT NULL foreign keys.

Written by the indexing model from the issue text.