fix(chart): keep zero-year chara and ephemeris dates apart

A zero-year Chara period is shown as 0 years instead of failing the whole chart. Switching ephemeris dates drops the previous day immediately and can be retried. Missing birth data links to chart settings.

frontend/src/app/(app)/page.tsx

@@ -499,7 +499,8 @@ export default function Home() {
     const applySettingsFromSearch = (search: string) => {
       const query = parseSettingsQuery(search);
       if (!query) return;
-      openAccountDialog("billing", { source: query.source ?? undefined, plan: query.plan ?? undefined, tab: query.tab ?? undefined });
+      if (query.pane === "chart") openAccountDialog("chart-library");
+      else openAccountDialog("billing", { source: query.source ?? undefined, plan: query.plan ?? undefined, tab: query.tab ?? undefined });
       const next = stripSettingsQuery(search, window.location.pathname);
       if (`${window.location.pathname}${window.location.search}` !== next) window.history.replaceState(null, "", next);
     };

frontend/src/app/api/ephemeris/route.ts

@@ -1,5 +1,6 @@
 import { NextResponse } from "next/server";
 
+import { chartViewEngineCacheKey, readChartViewEngineCache, writeChartViewEngineCache } from "@/lib/chart-view-engine";
 import { calendarDateInTimeZone } from "@/lib/daily-starlanguage";
 import { ephemerisIsoDateSchema, ephemerisOkResponseSchema, type EphemerisOkResponse } from "@/lib/ephemeris-contract";
 import {
@@ -23,18 +24,54 @@ const engineTimeoutMs = 20_000;
 type Profile = ReturnType<typeof globalBirthProfileFromAccountRow>;
 type BirthPayload = NonNullable<Awaited<ReturnType<typeof dailyProfilePayload>>>;
 
-async function fetchEngine(path: string, body: Record<string, unknown>) {
+function engineSignal(request: Request): AbortSignal {
+  return AbortSignal.any([AbortSignal.timeout(engineTimeoutMs), request.signal]);
+}
+
+async function fetchEngine(path: string, body: Record<string, unknown>, signal: AbortSignal) {
   const response = await fetch(`${jyotishApiBase}${path}`, {
     method: "POST",
     headers: { "Content-Type": "application/json" },
     body: JSON.stringify(body),
     cache: "no-store",
-    signal: AbortSignal.timeout(engineTimeoutMs),
+    signal,
   });
   if (!response.ok) throw new Error(`jyotish_api_${response.status}`);
   return await response.json() as unknown;
 }
 
+function natalCacheKey(userId: string, birth: BirthPayload): string {
+  const month = String(birth.month).padStart(2, "0");
+  const day = String(birth.day).padStart(2, "0");
+  const hour = String(birth.hour).padStart(2, "0");
+  const minute = String(birth.minute).padStart(2, "0");
+  return chartViewEngineCacheKey({
+    userId,
+    date: `${birth.year}-${month}-${day}`,
+    time: `${hour}:${minute}`,
+    latitude: birth.lat,
+    longitude: birth.lon,
+    timezoneOffset: birth.tz,
+    ayanamsa: birth.ayanamsa,
+    nodeMode: birth.node_mode,
+    path: "/api/ephemeris/natal-chart",
+  });
+}
+
+async function fetchNatalChart(userId: string, birth: BirthPayload, signal: AbortSignal): Promise<unknown> {
+  const key = natalCacheKey(userId, birth);
+  const hit = readChartViewEngineCache(key);
+  if (hit) return hit;
+  const payload = await fetchEngine("/api/chart", {
+    ...birth,
+    skip_vedastro_main_entry_overview: true,
+  }, signal);
+  if (!signal.aborted && payload && typeof payload === "object" && !Array.isArray(payload)) {
+    writeChartViewEngineCache(key, payload as Record<string, unknown>);
+  }
+  return payload;
+}
+
 function requestedDate(request: Request, timezoneId?: string | null): string {
   const raw = new URL(request.url).searchParams.get("date")?.trim() ?? "";
   if (raw && isEphemerisIsoDate(raw) && ephemerisIsoDateSchema.safeParse(raw).success) return raw;
@@ -75,6 +112,7 @@ export async function GET(request: Request) {
   const birth = await dailyProfilePayload(profile, date).catch(() => null);
   const location = locationBody(profile);
 
+  const signal = engineSignal(request);
   const panchangaBody: Record<string, unknown> = { start_date: date, end_date: date };
   if (location) {
     panchangaBody.lat = location.lat;
@@ -82,23 +120,20 @@ export async function GET(request: Request) {
     panchangaBody.tz = location.tz;
   }
 
-  const panchangaPromise = fetchEngine("/api/panchanga_range", panchangaBody).catch((error: unknown) => {
+  const panchangaPromise = fetchEngine("/api/panchanga_range", panchangaBody, signal).catch((error: unknown) => {
     console.warn("ephemeris_panchanga_unavailable", error);
     return null;
   });
 
   const natalPromise = birth
-    ? fetchEngine("/api/chart", {
-      ...birth,
-      skip_vedastro_main_entry_overview: true,
-    }).catch((error: unknown) => {
+    ? fetchNatalChart(user.id, birth, signal).catch((error: unknown) => {
       console.warn("ephemeris_natal_chart_unavailable", error);
       return null;
     })
     : Promise.resolve(null);
 
   const transitPromise = birth
-    ? fetchEngine("/api/chart", transitChartBody(birth, date)).catch((error: unknown) => {
+    ? fetchEngine("/api/chart", transitChartBody(birth, date), signal).catch((error: unknown) => {
       console.warn("ephemeris_transit_chart_unavailable", error);
       return null;
     })
@@ -109,7 +144,7 @@ export async function GET(request: Request) {
     end_date: addDaysIso(date, 90),
     ayanamsa: birth?.ayanamsa ?? profile.ayanamsa ?? "raman",
     node_mode: "mean",
-  }).catch((error: unknown) => {
+  }, signal).catch((error: unknown) => {
     console.warn("ephemeris_events_unavailable", error);
     return null;
   });

frontend/src/app/globals.css

@@ -2193,6 +2193,9 @@ input:not([type="radio"]):not([type="checkbox"]):not([class^="ant-"]):not([class
   font-size: var(--type-title-lg);
   font-weight: 500;
 }
+.chart-page-message h2 {
+  font-size: var(--type-title-md);
+}
 
 @media (max-width: 767px) {
   /* Replaces the three `*-shell { padding-inline }` rules the standalone pages