feat(topics): compute topic overviews and topic pages on the server

GET /api/topics answers one entry per topic the record holds data for:
a headline value, a rule-based sentence and a 30-day sparkline.
GET /api/topics/{topic} answers a topic's signals with their usual
ranges, side-by-side series for a chosen window, the relationships
between its signals, 90-day trends, what it holds nothing for yet, and
its blocks (training load, lab markers with their trend, screener
trends, the cycle day).

Every figure comes from reads the metric pages already make: the local
daily values, the reconstructed nights, the mood score, computeLabTrend,
the training load and the screener trends. No model is involved. A
relationship says nothing below 14 paired days and is only called a
pattern at p < 0.05; a lab trend needs three readings spanning a year.

The preview is the viewer's own opt-in: with it off both routes answer
404 topics.preview_off. Topics, signals and blocks follow the record's
module switches and the sections the viewer's grant opens; the routes
read across sections, so a scoped grant is refused like the timeline.
/api/auth/me publishes the caller's opt-ins as previewFeatures.

src/app/api/auth/me/route.ts

@@ -44,6 +44,7 @@
 import { apiSuccess } from "@/lib/api-response";
 import { apiHandler, requireActorAuth } from "@/lib/api-handler";
 import { annotate } from "@/lib/logging/context";
+import { resolvePreviewFeatures } from "@/lib/settings/preview-features";
 import { setOnboardingPendingCookie } from "@/lib/auth/session";
 import { syncMfaEnrollCookie } from "@/lib/auth/mfa-enrollment";
 import { buildAvatarUrl } from "@/lib/avatar";
@@ -93,6 +94,21 @@ const SERVER_FEATURES = {
   lifeCircumstances: true,
 } as const;
 
+/**
+ * v1.7.0 — patient-identity fields for the health-record export. The KVNR is
+ * stored encrypted; decrypt fail-soft so a key-rotation gap on one row never
+ * 500s the whole profile fetch (the field just reads null and the user
+ * re-enters it).
+ */
+function decryptInsuranceNumber(encrypted: string | null): string | null {
+  if (!encrypted) return null;
+  try {
+    return decrypt(encrypted);
+  } catch {
+    return null;
+  }
+}
+
 export const GET = apiHandler(async () => {
   const auth = await requireActorAuth();
   const { user } = auth;
@@ -238,10 +254,11 @@ export const GET = apiHandler(async () => {
     }),
     // The encrypted insurance number is not on the per-request user
     // (`SESSION_USER_SELECT`); it is read here, for the one response that
-    // shows it.
+    // shows it. The preview opt-ins ride the same point read of the caller's
+    // own row.
     prisma.user.findUnique({
       where: { id: user.id },
-      select: { insuranceNumberEncrypted: true },
+      select: { insuranceNumberEncrypted: true, previewFeaturesJson: true },
     }),
   ]);
 
@@ -289,18 +306,9 @@ export const GET = apiHandler(async () => {
     sectionsOpen(sections, "cycle") &&
     isCycleEnabled(record?.gender ?? null, cycleProfile);
 
-  // v1.7.0 — patient-identity fields for the health-record export. The
-  // KVNR is stored encrypted; decrypt fail-soft so a key-rotation gap on
-  // one row never 500s the whole profile fetch (the field just reads
-  // null and the user re-enters it).
-  let insuranceNumber: string | null = null;
-  if (identity?.insuranceNumberEncrypted) {
-    try {
-      insuranceNumber = decrypt(identity.insuranceNumberEncrypted);
-    } catch {
-      insuranceNumber = null;
-    }
-  }
+  const insuranceNumber = decryptInsuranceNumber(
+    identity?.insuranceNumberEncrypted ?? null,
+  );
 
   return apiSuccess({
     id: user.id,
@@ -447,6 +455,12 @@ export const GET = apiHandler(async () => {
     // `offIsReal` whether the lowest option is a real off or "Minimal", and
     // `source` which layer decided. Clients never recompute it.
     coachReasoning,
+    // The caller's own preview opt-ins (Settings > System > Preview
+    // features), resolved: every flag present, off unless switched on. The
+    // navigation offers the Topics entry from `topics`. The ACTOR's, like the
+    // Coach preferences above, so it does not move under a switch: a preview is
+    // chrome of the person reading, never a property of the record on screen.
+    previewFeatures: resolvePreviewFeatures(identity?.previewFeaturesJson),
     // v1.36.0 — account sharing, resolved. `accounts` is the switcher's menu,
     // `active` is the record this session is inside (null when it is in its
     // own), `canSwitch` and per-entry `canWrite` are the booleans the UI binds