Consolidate server utilities into shared module

- Add lib/server/utils/normalize.ts with normalizeTicker, normalizeTagsOrNull, nowIso, todayIso
- Add lib/server/utils/validation.ts with asRecord, asBoolean, asStringArray, asEnum
- Add lib/server/utils/index.ts re-exporting all utilities
- Remove duplicate lib/server/utils.ts (old file)
- Update all repos and files to use shared utilities
- Remove redundant ?? '' from normalizeTicker calls
- Update watchlist.ts to use normalizeTagsOrNull for null-return tags

lib/server/utils/normalize.ts

@@ -0,0 +1,51 @@
+export function normalizeTicker(ticker: string): string {
+  return ticker.trim().toUpperCase();
+}
+
+export function normalizeTickerOrNull(ticker: unknown): string | null {
+  if (typeof ticker !== 'string') return null;
+  const normalized = ticker.trim().toUpperCase();
+  return normalized || null;
+}
+
+export function normalizeTags(tags?: unknown): string[] {
+  if (!Array.isArray(tags)) return [];
+
+  const unique = new Set<string>();
+  for (const entry of tags) {
+    if (typeof entry !== 'string') continue;
+    const tag = entry.trim();
+    if (tag) unique.add(tag);
+  }
+  return [...unique];
+}
+
+export function normalizeTagsOrNull(tags?: unknown): string[] | null {
+  const result = normalizeTags(tags);
+  return result.length > 0 ? result : null;
+}
+
+export function normalizeOptionalString(value?: unknown): string | null {
+  if (typeof value !== 'string') return null;
+  const normalized = value.trim();
+  return normalized || null;
+}
+
+export function normalizeRecord(value?: unknown): Record<string, unknown> | null {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) return null;
+  return value as Record<string, unknown>;
+}
+
+export function normalizePositiveInteger(value?: unknown): number | null {
+  if (value === null || value === undefined || !Number.isFinite(value as number)) return null;
+  const normalized = Math.trunc(value as number);
+  return normalized > 0 ? normalized : null;
+}
+
+export function nowIso(): string {
+  return new Date().toISOString();
+}
+
+export function todayIso(): string {
+  return new Date().toISOString().slice(0, 10);
+}