chore: add pre-commit hooks, tighten ESLint, activate Sentry DSN, publish CI coverage (Phase 1)

- Install husky v9 + lint-staged: pre-commit runs eslint --fix and prettier on staged files
- Tighten ESLint base config: no-console→error, ban-ts-comment (ts-ignore banned, ts-expect-error with description allowed), reportUnusedDisableDirectives→error
- Migrate web app from deprecated `next lint` to `eslint src/` with flat config and react-hooks plugin
- Convert all 5 @ts-ignore to @ts-expect-error with descriptions, remove stale disable comments
- Add NEXT_PUBLIC_SENTRY_DSN to docker-compose.prod.yml and .env.example
- Add coverage artifact upload step to CI test job
- Pre-existing violations (102 warnings) downgraded to warn in web config for Phase 2 cleanup

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/hooks/useTimelineLayout.tsx

@@ -35,23 +35,29 @@ export function useTimelineLayout(
   );
 
   // Grid lines — memoized; identical for every row
-  const gridLines = useMemo(() => dates.map((date, i) => {
-    const isToday = date.toDateString() === today.toDateString();
-    const dow = date.getDay();
-    const isWeekend = dow === 0 || dow === 6;
-    return (
-      <div
-        key={i}
-        className={clsx(
-          "absolute top-0 bottom-0 border-r",
-          isToday ? "border-brand-300 dark:border-brand-700 border-r-2" :
-          isWeekend ? "border-brand-200 dark:border-brand-800 bg-brand-50/40 dark:bg-brand-950/20" :
-          "border-gray-100 dark:border-gray-800",
-        )}
-        style={{ left: i * CELL_WIDTH, width: CELL_WIDTH }}
-      />
-    );
-  }), [dates, CELL_WIDTH, today]); // eslint-disable-line react-hooks/exhaustive-deps
+  const gridLines = useMemo(
+    () =>
+      dates.map((date, i) => {
+        const isToday = date.toDateString() === today.toDateString();
+        const dow = date.getDay();
+        const isWeekend = dow === 0 || dow === 6;
+        return (
+          <div
+            key={i}
+            className={clsx(
+              "absolute top-0 bottom-0 border-r",
+              isToday
+                ? "border-brand-300 dark:border-brand-700 border-r-2"
+                : isWeekend
+                  ? "border-brand-200 dark:border-brand-800 bg-brand-50/40 dark:bg-brand-950/20"
+                  : "border-gray-100 dark:border-gray-800",
+            )}
+            style={{ left: i * CELL_WIDTH, width: CELL_WIDTH }}
+          />
+        );
+      }),
+    [dates, CELL_WIDTH, today],
+  );
 
   // Month groups for the month header
   const monthGroups = useMemo(() => {
@@ -72,5 +78,15 @@ export function useTimelineLayout(
     return dates[colIndex] ?? today;
   }
 
-  return { CELL_WIDTH, dates, visibleDays, totalCanvasWidth, toLeft, toWidth, gridLines, monthGroups, xToDate };
+  return {
+    CELL_WIDTH,
+    dates,
+    visibleDays,
+    totalCanvasWidth,
+    toLeft,
+    toWidth,
+    gridLines,
+    monthGroups,
+    xToDate,
+  };
 }