feat(settings): a time-format preference and one home for insight pills

The clock format followed the UI language with no way out — an English
interface forced AM/PM everywhere. A new profile preference (automatic,
24-hour, 12-hour) feeds every formatter through the shared locale
context, persists on the user row and rides the profile endpoints. The
insight pill list in settings gains the same eye toggle the overview
tiles have, so ordering and visibility live in one place; the page-side
'manage detail pages' block folds into a link there. Includes the
locale bundles for both features and the regenerated API contract.

prisma/migrations/0138_v11520_time_format/migration.sql

@@ -0,0 +1,14 @@
+-- v1.15.20 — per-user hour-cycle display preference.
+--
+-- The UI locale alone decided whether times rendered as AM/PM or 24-hour,
+-- which left e.g. an en-locale user no way to read 24-hour times. The new
+-- column carries an explicit preference: AUTO follows the locale convention,
+-- H12 forces AM/PM, H24 forces 24-hour. Display-time only — stored instants
+-- stay UTC.
+--
+-- Additive + non-destructive: a new NOT NULL column with a default, no
+-- backfill needed. Existing rows read AUTO.
+CREATE TYPE "time_format_preference" AS ENUM ('AUTO', 'H12', 'H24');
+
+ALTER TABLE "users"
+  ADD COLUMN "time_format" "time_format_preference" NOT NULL DEFAULT 'AUTO';

prisma/schema.prisma

@@ -132,6 +132,10 @@ model User {
   // Canonical storage stays SI; this only selects the display-time
   // transform branch (km/h vs mph, km vs mi). Null = default "metric".
   unitPreference          String? @map("unit_preference") // "metric" | "imperial" | null = default "metric"
+  // Hour-cycle display preference. AUTO follows the locale convention
+  // (en → AM/PM, de → 24h), H12 forces AM/PM, H24 forces 24-hour.
+  // Display-time only — canonical storage stays UTC instants.
+  timeFormat              TimeFormatPreference @default(AUTO) @map("time_format")
   // AI provider selection for insights. Null = OPENAI fallback.
   aiProvider              String? @map("ai_provider") // "OPENAI" | "ANTHROPIC" | "LOCAL" | "CHATGPT_OAUTH"
   aiModel                 String? @map("ai_model")
@@ -716,6 +720,16 @@ enum GlucoseContext {
   @@map("glucose_context")
 }
 
+// Hour-cycle display preference for rendered times. AUTO defers to the
+// active locale's convention; H12/H24 pin the cycle regardless of locale.
+enum TimeFormatPreference {
+  AUTO
+  H12
+  H24
+
+  @@map("time_format_preference")
+}
+
 enum MeasurementSource {
   MANUAL
   WITHINGS