Teaching: hide-notes-until share, session length check, slides export

- A study share link can hide the owner's notes until a chosen time: the server
  sends only passages and discussion questions until then, with a banner in the
  shared view (new share_reveal column, migrated on start).
- Outline: a session length with "N of M min planned, X min over" and a marker
  on the point where the plan runs past it.
- Export > Slides: printable 16:9 slides (title, passage, outline points with
  their verse, discussion questions) for one session or all; light or dark.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/db.js

@@ -140,7 +140,7 @@ export function initDb() {
     db.exec('ALTER TABLE projects ADD COLUMN outline_share_token TEXT');
   }
   // Share links can expire and be protected by a passcode.
-  for (const col of ['share_expires INTEGER', 'share_pass TEXT', 'outline_share_expires INTEGER', 'outline_share_pass TEXT']) {
+  for (const col of ['share_expires INTEGER', 'share_pass TEXT', 'share_reveal INTEGER', 'outline_share_expires INTEGER', 'outline_share_pass TEXT']) {
     if (!projectCols.some((c) => c.name === col.split(' ')[0])) db.exec(`ALTER TABLE projects ADD COLUMN ${col}`);
   }
   db.exec('CREATE UNIQUE INDEX IF NOT EXISTS idx_projects_outline_share_token ON projects(outline_share_token) WHERE outline_share_token IS NOT NULL');
@@ -780,7 +780,7 @@ export function setShareToken(id, userId, token) {
 
 /** Revokes a project's share link, scoped to userId. */
 export function clearShareToken(id, userId) {
-  db.prepare('UPDATE projects SET share_token = NULL, share_expires = NULL, share_pass = NULL WHERE id = ? AND user_id = ?').run(id, userId);
+  db.prepare('UPDATE projects SET share_token = NULL, share_expires = NULL, share_pass = NULL, share_reveal = NULL WHERE id = ? AND user_id = ?').run(id, userId);
 }
 
 // ---- read-only outline links: a separate token, so sharing an outline never shares the whole study ----
@@ -800,14 +800,14 @@ export function clearOutlineShareToken(id, userId) {
 
 // ---- expiry and passcode for either kind of read-only link (outline = the outline-only link) ----
 const shareCols = (outline) => (outline
-  ? { token: 'outline_share_token', expires: 'outline_share_expires', pass: 'outline_share_pass' }
-  : { token: 'share_token', expires: 'share_expires', pass: 'share_pass' });
+  ? { token: 'outline_share_token', expires: 'outline_share_expires', pass: 'outline_share_pass', reveal: 'NULL' }
+  : { token: 'share_token', expires: 'share_expires', pass: 'share_pass', reveal: 'share_reveal' });
 
-/** { token, expiresAt, hasPasscode } for the owner's link settings. */
+/** { token, expiresAt, hasPasscode, revealAt } for the owner's link settings (revealAt: notes stay hidden until then). */
 export function getShareSettings(id, userId, outline = false) {
   const c = shareCols(outline);
-  const row = db.prepare(`SELECT ${c.token} AS token, ${c.expires} AS expiresAt, ${c.pass} AS pass FROM projects WHERE id = ? AND user_id = ?`).get(id, userId);
-  return row ? { token: row.token ?? null, expiresAt: row.expiresAt ?? null, hasPasscode: !!row.pass } : null;
+  const row = db.prepare(`SELECT ${c.token} AS token, ${c.expires} AS expiresAt, ${c.pass} AS pass, ${c.reveal} AS revealAt FROM projects WHERE id = ? AND user_id = ?`).get(id, userId);
+  return row ? { token: row.token ?? null, expiresAt: row.expiresAt ?? null, hasPasscode: !!row.pass, revealAt: row.revealAt ?? null } : null;
 }
 
 /** The stored passcode hash of a link (kept when only the expiry is changed). */
@@ -816,18 +816,20 @@ export function getSharePassHash(id, userId, outline = false) {
   return db.prepare(`SELECT ${c.pass} AS pass FROM projects WHERE id = ? AND user_id = ?`).get(id, userId)?.pass ?? null;
 }
 
-/** Sets expiry (ms timestamp or null) and passcode hash (or null) on an existing link. */
-export function setShareSettings(id, userId, { expiresAt, passHash }, outline = false) {
+/** Sets expiry (ms timestamp or null), passcode hash (or null) and, for a study link, when its notes appear (or null). */
+export function setShareSettings(id, userId, { expiresAt, passHash, revealAt }, outline = false) {
   const c = shareCols(outline);
-  return db.prepare(`UPDATE projects SET ${c.expires} = ?, ${c.pass} = ? WHERE id = ? AND user_id = ?`).run(expiresAt ?? null, passHash ?? null, id, userId).changes > 0;
+  const changed = db.prepare(`UPDATE projects SET ${c.expires} = ?, ${c.pass} = ? WHERE id = ? AND user_id = ?`).run(expiresAt ?? null, passHash ?? null, id, userId).changes > 0;
+  if (changed && !outline && revealAt !== undefined) db.prepare('UPDATE projects SET share_reveal = ? WHERE id = ? AND user_id = ?').run(revealAt ?? null, id, userId);
+  return changed;
 }
 
 /** Public lookup for a link: the project plus the link's rules, or null for an unknown token. */
 export function getSharedByToken(token, outline = false) {
   const c = shareCols(outline);
-  const row = db.prepare(`SELECT data, ${c.expires} AS expiresAt, ${c.pass} AS passHash FROM projects WHERE ${c.token} = ?`).get(token);
+  const row = db.prepare(`SELECT data, ${c.expires} AS expiresAt, ${c.pass} AS passHash, ${c.reveal} AS revealAt FROM projects WHERE ${c.token} = ?`).get(token);
   if (!row) return null;
-  try { return { project: JSON.parse(row.data), expiresAt: row.expiresAt ?? null, passHash: row.passHash ?? null }; } catch { return null; }
+  try { return { project: JSON.parse(row.data), expiresAt: row.expiresAt ?? null, passHash: row.passHash ?? null, revealAt: row.revealAt ?? null }; } catch { return null; }
 }
 
 /** Public lookup: the project data behind an outline link (callers must only ever send the outlines on). */