fix sync reliability and runtime handling

tests/config.test.ts

@@ -31,4 +31,8 @@ describe("loadConfig", () => {
     const config = loadConfig({ BOT_MODE: "http-only", ENABLE_FDS_SLEEP_DETAILS: "false" });
     expect(config.ENABLE_FDS_SLEEP_DETAILS).toBe(false);
   });
+
+  test("rejects an invalid timezone", () => {
+    expect(() => loadConfig({ BOT_MODE: "http-only", TZ: "not/a-timezone" })).toThrow(ConfigurationError);
+  });
 });

tests/formatting.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { esc, minutes, stepBar } from "../src/bot/formatting.js";
+import { epoch, esc, minutes, stepBar } from "../src/bot/formatting.js";
 
 describe("bot formatting", () => {
   test("escapes Telegram HTML and formats health values", () => {
@@ -7,4 +7,10 @@ describe("bot formatting", () => {
     expect(minutes(396)).toBe("6 h 36 min");
     expect(stepBar(5000)).toContain("50%");
   });
+
+  test("formats timestamps in the configured timezone", () => {
+    const timestamp = Date.parse("2026-08-12T00:00:00Z") / 1000;
+    expect(epoch(timestamp, false, "en", "UTC")).toContain("00:00");
+    expect(epoch(timestamp, false, "en", "Europe/Moscow")).toContain("03:00");
+  });
 });

tests/secure-files.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { mkdtempSync, rmSync } from "node:fs";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import { withExclusiveFileLock } from "../src/storage/secure-files.js";
 
@@ -11,4 +11,13 @@ describe("file locks", () => {
     await expect(withExclusiveFileLock(path, async () => "second")).resolves.toBe("second");
     rmSync(directory, { recursive: true, force: true });
   });
+
+  test("reclaims a lock whose owner process is gone", async () => {
+    const directory = mkdtempSync(join(process.env.TMPDIR ?? "/tmp", "miband-lock-stale-"));
+    const path = join(directory, "sync.lock");
+    mkdirSync(`${path}.d`);
+    writeFileSync(join(`${path}.d`, "owner"), "pid=2147483647 time=0\n");
+    await expect(withExclusiveFileLock(path, async () => "reclaimed")).resolves.toBe("reclaimed");
+    rmSync(directory, { recursive: true, force: true });
+  });
 });