Expose maxPriority in keypair resource policy settings

## Background

26.8.0 adds `maxPriority: Int` to `KeypairResourcePolicyV2` (+ create/update inputs and filter): the highest **global** scheduling `priority` a session created with this policy may declare. `null` = uncapped; DB CHECK constrains 0–100. Note this caps the global queue `priority`, NOT the preemption `jobPriority` (deliberately uncapped in core since its default victim scope is the user's own sessions).

## Scope

1. `KeypairResourcePolicyV2SettingModal`: nullable Int input (0–100, empty = unlimited) with copy explaining it caps the session queue priority.
1. Show the value in the policy list/info views.

## Acceptance criteria

- Field round-trips including the null (unlimited) case; `bash scripts/verify.sh` passes.

JIRA Issue: FR-3891

Start at KeypairResourcePolicyV2SettingModal and trace the existing policy create/update and filter fields into the policy list and info views. Run bash scripts/verify.sh while checking the nullable 0–100 input and its round-trip behavior. Done means the setting is explained as capping global session queue priority, displayed in both views, and preserves null as unlimited.

Written by the indexing model from the issue text.