fix(audit): wire reminder defaults into createInterest; doc branding gap (R2-H15/H16)

R2-H16: /admin/reminders persisted defaultEnabled + defaultDays to
system_settings but createInterest ignored them — every new interest
defaulted to reminderEnabled=false regardless. The validator now
treats reminderEnabled / reminderDays as optional (no default false),
and createInterest falls back to getPortReminderConfig(portId) when
the caller omits them. Explicit false / null still opts out.

R2-H15: branding admin (/admin/branding) saves 5 settings that no
code reads — the email templates and BrandedAuthShell hardcode Port
Nimara branding. Wiring it end-to-end is a multi-template refactor;
documented the gap inline above getPortBrandingConfig with a
step-by-step wire-up plan so future devs don't think it's done.

The reminder-digest scheduler (digestEnabled/digestTime/digestTimezone)
remains unimplemented — needs a new BullMQ recurring job that batches
pending reminders into per-user/per-port digest emails. Out of scope
for this audit pass.

1175/1175 vitest passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/validators/interests.ts

@@ -35,7 +35,10 @@ export const createInterestSchema = z.object({
   source: z.string().optional(),
   notes: z.string().optional(),
   tagIds: z.array(z.string()).optional().default([]),
-  reminderEnabled: z.boolean().optional().default(false),
+  // Omitting reminderEnabled / reminderDays falls back to the per-port
+  // defaults configured at /admin/reminders (resolved in
+  // createInterest). To opt out explicitly pass false / null.
+  reminderEnabled: z.boolean().optional(),
   reminderDays: z.number().int().min(1).optional(),
   desiredLengthFt: optionalDesiredDimSchema,
   desiredWidthFt: optionalDesiredDimSchema,