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/index.ts

@@ -0,0 +1,20 @@
+export {
+  normalizeTicker,
+  normalizeTickerOrNull,
+  normalizeTags,
+  normalizeTagsOrNull,
+  normalizeOptionalString,
+  normalizeRecord,
+  normalizePositiveInteger,
+  nowIso,
+  todayIso
+} from './normalize';
+
+export {
+  asRecord,
+  asOptionalRecord,
+  asPositiveNumber,
+  asBoolean,
+  asStringArray,
+  asEnum
+} from './validation';