Add devMode for NAC widgets

[rchlfryn]

Summary

• Add NAC_WIDGET_DEV_MODE environment variable to control the devMode value passed to NAC widget configs
• When set to "true", overrides the production lock that currently forces devMode to false
• Falls back to the nacWidgetsConfig global's devMode field when the env var is not set
• Enables dedicated staging environments to point widgets at the staging base URL without code changes or redeployment

Motivation

Fixes #717

Currently, devMode is always forced to false in production (getNACWidgetsConfig.ts), regardless of the admin panel setting. This makes it impossible to run a staging/preview deployment that uses the NAC staging widget URLs — useful for nwacus/app (AvyApp) development and testing custom data entered in staging.

Changes

• src/utilities/getNACWidgetsConfig.ts — Check NAC_WIDGET_DEV_MODE env var before falling back to the global config value. Remove the blanket production override so staging deployments can opt in.
• .env.example — Document the new NAC_WIDGET_DEV_MODE variable.

How it works

Priority order for devMode:

1. NAC_WIDGET_DEV_MODE env var ("true" → true, "false" → false)
2. nacWidgetsConfig.devMode global value from admin panel
3. Defaults to false

Test plan

• Verify widgets load normally in local dev with no env var set (devMode respects admin panel)
• Set NAC_WIDGET_DEV_MODE=true and confirm widgets use the staging base URL
• Set NAC_WIDGET_DEV_MODE=false and confirm it overrides an admin panel devMode: true
• Verify production deployment without the env var still defaults to devMode: false
• Check /api/[center]/nac-config endpoint returns the correct devMode value

[github-actions]

Migration Safety Check

Found 1 potential issue:

20260304_201458_add_dev_mode.ts

Warning (line 6): ALTER keyword detected - review for data loss

sql`ALTER TABLE \`nac_widgets_config\` ADD \`dev_mode\` integer DEFAULT false NOT NULL;`,

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Review these patterns and add backup/restore logic if needed. See docs/migration-safety.md for guidance.

[github-actions]

Preview deployment: https://nac-dev.preview.avy-fx.org

[rchlfryn]

@busbyk Leaving this as a draft. It is ready fro review but I am curious if you think this is the correct approach based on the issue you wrote.