style(frontend): Prettier config + one-time repo-wide format pass

Prettier 3 (pinned), printWidth 100, double quotes — chosen to match the existing
hand-formatting and minimise reflow. This commit is ONLY the mechanical format pass
(`prettier --write`) plus the config/ignore/scripts, isolated so it never pollutes a
feature diff. Verified behaviour-neutral: typecheck, eslint (0 errors), and vitest
all green before and after. See .git-blame-ignore-revs — `git blame` skips this sha.

frontend/src/lib/descriptionLinks.tsx

@@ -14,9 +14,7 @@ const INLINE_RE =
 
 function tsToSeconds(ts: string): number {
   const parts = ts.split(":").map((n) => parseInt(n, 10));
-  return parts.length === 3
-    ? parts[0] * 3600 + parts[1] * 60 + parts[2]
-    : parts[0] * 60 + parts[1];
+  return parts.length === 3 ? parts[0] * 3600 + parts[1] * 60 + parts[2] : parts[0] * 60 + parts[1];
 }
 
 // Parse a YouTube `t`/`start` param: "90", "90s", or "1h2m3s".
@@ -26,9 +24,7 @@ function parseStart(t: string | null): number | null {
   const m = t.match(/^(?:(\d+)h)?(?:(\d+)m)?(?:(\d+)s)?$/);
   if (!m) return null;
   const total =
-    parseInt(m[1] || "0", 10) * 3600 +
-    parseInt(m[2] || "0", 10) * 60 +
-    parseInt(m[3] || "0", 10);
+    parseInt(m[1] || "0", 10) * 3600 + parseInt(m[2] || "0", 10) * 60 + parseInt(m[3] || "0", 10);
   return total || null;
 }
 
@@ -62,7 +58,7 @@ export function renderDescription(
     onSeek: (seconds: number) => void;
     onLoadVideo: (id: string, start: number | null) => void;
     t: TFunction;
-  }
+  },
 ): ReactNode[] {
   const { t } = opts;
   const out: ReactNode[] = [];
@@ -70,7 +66,10 @@ export function renderDescription(
   const linkCls = "text-accent hover:underline break-all";
   // Tidy YouTube descriptions: drop trailing spaces and remove blank lines entirely
   // (they're just noise in the popover), keeping single line breaks.
-  const clean = text.replace(/[ \t]+\n/g, "\n").replace(/\n{2,}/g, "\n").trim();
+  const clean = text
+    .replace(/[ \t]+\n/g, "\n")
+    .replace(/\n{2,}/g, "\n")
+    .trim();
   for (const chunk of clean.split(URL_RE)) {
     if (/^https?:\/\//.test(chunk)) {
       const href = chunk.replace(/[.,;:!?)\]]+$/, "");
@@ -87,13 +86,13 @@ export function renderDescription(
             title={sameVideo ? t("player.jumpToTime") : t("player.playInApp")}
           >
             {href}
-          </button>
+          </button>,
         );
       } else {
         out.push(
           <a key={key++} href={href} target="_blank" rel="noreferrer" className={linkCls}>
             {href}
-          </a>
+          </a>,
         );
       }
       continue;
@@ -110,9 +109,10 @@ export function renderDescription(
         out.push(
           <a key={key++} href={`mailto:${email}`} className={linkCls}>
             {email}
-          </a>
+          </a>,
         );
-        if (m[1].length > email.length) out.push(<span key={key++}>{m[1].slice(email.length)}</span>);
+        if (m[1].length > email.length)
+          out.push(<span key={key++}>{m[1].slice(email.length)}</span>);
       } else if (m[2]) {
         // Hashtag → YouTube's hashtag feed (mirrors native YouTube behavior).
         const tag = m[2].slice(1);
@@ -125,7 +125,7 @@ export function renderDescription(
             className={linkCls}
           >
             {m[2]}
-          </a>
+          </a>,
         );
       } else {
         const ts = m[3];
@@ -136,7 +136,7 @@ export function renderDescription(
             className="text-accent hover:underline"
           >
             {ts}
-          </button>
+          </button>,
         );
       }
       last = m.index + m[0].length;