refactor: consolidate duplicated code across web and API packages

- Extract shared render helpers (vacation blocks, range overlay, overbooking blink) into renderHelpers.tsx
- Centralize status badge styles and vacation color maps into status-styles.ts
- Extract dragMath.ts utility from useTimelineDrag for reuse
- Split useInvalidatePlanningViews into useInvalidateTimeline (4 queries) + useInvalidatePlanningViews (8 queries)
- Adopt findUniqueOrThrow() and Prisma select constants across API routers
- Add shared fmtEur() helper for API-side money formatting
- Wrap TimelineResourcePanel and TimelineProjectPanel with React.memo
- Fix pre-existing TS2589 deep type errors in TeamCalendar and VacationModal
- 38 files changed, reducing ~400 lines of duplicated code

Co-Authored-By: claude-flow <ruv@ruv.net>

packages/api/src/router/computation-graph.ts

@@ -12,6 +12,7 @@ import type { CalculationRule, AbsenceDay, SpainScheduleRule, WeekdayAvailabilit
 import { VacationStatus } from "@planarchy/db";
 import { z } from "zod";
 import { createTRPCRouter, controllerProcedure } from "../trpc.js";
+import { fmtEur } from "../lib/format-utils.js";
 
 // ─── Graph Types (mirrored from client for API response) ────────────────────
 
@@ -50,10 +51,6 @@ function l(source: string, target: string, formula: string, weight = 1): GraphLi
   return { source, target, formula, weight };
 }
 
-function fmtEur(cents: number): string {
-  return `${(cents / 100).toLocaleString("de-DE", { minimumFractionDigits: 2 })} EUR`;
-}
-
 function fmtPct(ratio: number): string {
   return `${(ratio * 100).toFixed(1)}%`;
 }