Rebuild PDF generation: HTML <table> + Playwright replaces PDFKit manual drawing

Task #372: Replaced the manual PDFKit coordinate-based PDF renderer with an
HTML table-based approach using Playwright's headless Chromium.

Key changes:
- Created `pdf-html-renderer.ts` with `buildScheduleHtml()` (generates full
  HTML with embedded base64 fonts, proper `<table>`, RTL/LTR support, row
  colors, merged cells, attendees formatting) and `htmlToPdfBuffer()` (renders
  HTML to PDF via Playwright Chromium).
- Updated `pdf-renderer.ts`: `renderSchedulePdf()` now delegates to the new
  HTML renderer via dynamic import. Legacy PDFKit code preserved as
  `renderSchedulePdf_LEGACY()` for fallback reference.
- Added `playwright-core` dependency and configured esbuild externals.
- Proper TypeScript types: `TableCell` interface for cell models, `Browser`
  type from playwright-core for browser instance management.
- Chromium provisioning: searches `.cache/ms-playwright/` with env var override
  (`PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH`), auto-installs via
  `npx playwright-core install chromium` if not found.
- Browser singleton with launch mutex to prevent concurrent double-launch,
  plus process shutdown hook to close browser on exit.

Requirements met:
- Each meeting in exactly one `<tr>` with 4 `<td>` cells
- No text outside table, attendees ~3 per line inline
- Time always in its column, `page-break-inside: avoid`, `table-layout: fixed`
- Matches reference design (blue header, centered text, DIN Next LT Arabic)

artifacts/api-server/src/lib/pdf-html-renderer.ts

@@ -1,9 +1,18 @@
 import { fileURLToPath } from "node:url";
 import path from "node:path";
 import { readFileSync, existsSync, readdirSync } from "node:fs";
+import { execSync } from "node:child_process";
 import sanitizeHtml from "sanitize-html";
+import type { Browser } from "playwright-core";
 import type { RenderPdfInput, PdfMeeting, PdfMeetingAttendee } from "./pdf-renderer.js";
 
+interface TableCell {
+  html: string;
+  cls: string;
+  style: string;
+  colspan?: number;
+}
+
 const ROW_COLOR_FILL: Record<string, string> = {
   red: "#fee2e2",
   amber: "#fef3c7",
@@ -195,20 +204,28 @@ function buildMeetingRow(meeting: PdfMeeting, input: RenderPdfInput): string {
     number: 0, meeting: 1, attendees: 2, time: 3,
   };
 
-  let cellsLtr = [
+  const cellsLtr: TableCell[] = [
     { html: esc(String(meeting.dailyNumber)), cls: "num-cell", style: "" },
     { html: esc(title) + location, cls: "meeting-cell", style: "" },
     { html: attendeesHtml, cls: "attendees-cell", style: "" },
     { html: `<span dir="ltr">${esc(time)}</span>`, cls: "time-cell", style: "" },
   ];
 
+  const renderCells = (cells: TableCell[]): string =>
+    cells
+      .map((c) => {
+        const cs = c.colspan ? ` colspan="${c.colspan}"` : "";
+        return `<td class="${c.cls}" style="${bgStyle}${c.style}"${cs}>${c.html}</td>`;
+      })
+      .join("");
+
   if (meeting.mergeStartColumn && meeting.mergeEndColumn) {
     const startIdx = MERGE_COL_INDEX[meeting.mergeStartColumn];
     const endIdx = MERGE_COL_INDEX[meeting.mergeEndColumn];
     if (startIdx !== undefined && endIdx !== undefined && startIdx <= endIdx) {
       const colspan = endIdx - startIdx + 1;
       const mergeText = meeting.mergeText ? htmlToPlain(meeting.mergeText) : "";
-      const mergedCell = {
+      const mergedCell: TableCell = {
         html: esc(mergeText),
         cls: "merged-cell",
         style: "",
@@ -216,32 +233,20 @@ function buildMeetingRow(meeting: PdfMeeting, input: RenderPdfInput): string {
       };
       const before = cellsLtr.slice(0, startIdx);
       const after = cellsLtr.slice(endIdx + 1);
-      const merged = [...before, mergedCell, ...after];
+      const merged: TableCell[] = [...before, mergedCell, ...after];
 
       const cells = isRtl ? [...merged].reverse() : merged;
-      const tds = cells
-        .map((c: any) => {
-          const cs = c.colspan ? ` colspan="${c.colspan}"` : "";
-          return `<td class="${c.cls}" style="${bgStyle}${c.style}"${cs}>${c.html}</td>`;
-        })
-        .join("");
-      return `<tr style="${bgStyle}">${tds}</tr>`;
+      return `<tr style="${bgStyle}">${renderCells(cells)}</tr>`;
     }
   }
 
   const cells = isRtl ? [...cellsLtr].reverse() : cellsLtr;
-  const tds = cells
-    .map(
-      (c) => `<td class="${c.cls}" style="${bgStyle}${c.style}">${c.html}</td>`,
-    )
-    .join("");
-  return `<tr style="${bgStyle}">${tds}</tr>`;
+  return `<tr style="${bgStyle}">${renderCells(cells)}</tr>`;
 }
 
 export function buildScheduleHtml(input: RenderPdfInput): string {
   const isRtl = input.lang === "ar";
   const dir = isRtl ? "rtl" : "ltr";
-  const fontFamily = input.font.fontFamily === "system" ? "ScheduleFont" : input.font.fontFamily;
   const fontSize = input.font.fontSize;
   const fontWeight = input.font.fontWeight === "bold" ? "bold" : "normal";
   const fontColor = input.font.fontColor || "#000000";
@@ -450,8 +455,8 @@ tr {
 </html>`;
 }
 
-let browserInstance: any = null;
-let launchPromise: Promise<any> | null = null;
+let browserInstance: Browser | null = null;
+let launchPromise: Promise<Browser> | null = null;
 
 function findChromiumExecutable(): string {
   if (process.env.PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH) {
@@ -492,7 +497,27 @@ function findChromiumExecutable(): string {
   );
 }
 
-async function getBrowser() {
+function ensureChromiumInstalled(): string {
+  try {
+    return findChromiumExecutable();
+  } catch {
+    try {
+      execSync("npx playwright-core install chromium", {
+        stdio: "pipe",
+        timeout: 120_000,
+      });
+      return findChromiumExecutable();
+    } catch (installErr) {
+      throw new Error(
+        `Chromium browser not found and auto-install failed. ` +
+        `Run "npx playwright-core install chromium" manually or set PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH. ` +
+        `Install error: ${installErr instanceof Error ? installErr.message : String(installErr)}`,
+      );
+    }
+  }
+}
+
+async function getBrowser(): Promise<Browser> {
   if (browserInstance && browserInstance.isConnected()) {
     return browserInstance;
   }
@@ -501,7 +526,7 @@ async function getBrowser() {
 
   launchPromise = (async () => {
     const { chromium } = await import("playwright-core");
-    const execPath = findChromiumExecutable();
+    const execPath = ensureChromiumInstalled();
 
     const browser = await chromium.launch({
       executablePath: execPath,