NodeLink Storage Region Spacing Fixes

Itemized suggestions from the Task 8306 visual check of the NodeLink storage forms: 1. In the Share dialog and the NodeLink Storage tab, Region is free text ("e.g. us-east-1"), while Settings › NodeLink storage offers it as a pick from the AWS region list. Offer the same region select in the tenant forms. 2. In the Share dialog (New AWS EFS), the Region field's hint row leaves an uneven gap between the AWS credential/Region row and the Subnet/Allowed CIDR row. Align the rows so hints do not offset neighbouring fields. 3. In Settings › NodeLink storage, a set location's "Policy written" fact sits alone on its own row with only "—". Hide it until a policy has been written, or fold it into the Policy fact. Out of scope: any API change; the radio-group wording from Task 8292. Done means: each item is implemented or explicitly rejected with a reason; `./dc check quick` is green; screenshots of the changed surfaces at desktop and ≤480px.

Region is now a pick from the AWS list on the Share dialog and Storage tab (one shared field). Hint rows no longer offset the grid, and Settings hides Policy written until a policy is written. Quick gate green. Checked at desktop and 390px. PR #6443 is queued in the lane. Follow-up draft 8391. Memory: used mem-15203.