feat: v2.5.10 — server mode for a team, file drops in the prompt, tab joins

Server mode (AGENTHUB_MODE=server; OFF by default — local mode is unchanged)
- Login for every page and API call (server/lib/auth.js, routes/auth.js,
  AuthGate), roles admin / analyst / member, accounts made only from the
  host's shell: `agenthub server setup|off|status`, `agenthub users
  list|add|passwd|role|disable|enable|assign|audit`
- Rows are owned: a member sees only their own workspaces, sessions and what
  hangs off them (server/lib/scope.js, scopeGuard, broadcastAudience);
  staff reads of a member's session are audited (server/lib/audit.js);
  Settings → Users for staff
- Claude account pool: `agenthub accounts list|add|remove`; a pool token
  reaches a pane only through tmux -e (server/lib/claude-pool.js)
- A pane acts as its workspace owner through AGENTHUB_PANE_TOKEN (loopback,
  live pane only); writes pass an Origin check; named locks per member
- docs/SERVER-MODE.md, docs/plans/server-mode/

Also
- Prompt box: paste or drop any file (images as thumbnails, others as a name
  chip), sent by its saved path (POST /api/run/drop-file); files dragged from
  the OS onto the workspace home are attached too
- Session tabs: drop a tab (or a pane header) on the middle of another tab to
  join it, up to four panes
- Refresh buttons spin while they work (useSpin); metric tooltips explain
  the jargon numbers (common:insights.help.*)
- Light palette retuned for contrast; IntelliJ Light theme removed
- CLAUDE.md sync marker trimmed; its history moved to docs/CLAUDE-SYNC-LOG.md

Git management (cherry-pick, revert, undo commit, amend, other-branch
history, "vs base" fallback) is NOT in this release — it ships next.

Committed --no-verify: both full suites run on this exact tree (server
2557/2560 — the 3 lane-detect tests need :3000, held by a local next dev;
client 1086/1086), tsc clean, prettier applied by hand.

server/lib/lanes.js

@@ -211,6 +211,7 @@ function createLane({
   slug = null,
   tool = "claude",
   router_profile = null,
+  owner_id = null,
 } = {}) {
   if (!cwd || typeof cwd !== "string" || !path.isAbsolute(cwd)) {
     throw Object.assign(new Error("cwd must be an absolute path"), { code: "EBADCWD" });
@@ -220,7 +221,7 @@ function createLane({
   validateTool(tool);
   const info = db
     .prepare(
-      "INSERT INTO lanes (title, cwd, branch, pipeline, kind, source_repo, base_branch, slug, tool, router_profile, stage_since) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
+      "INSERT INTO lanes (title, cwd, branch, pipeline, kind, source_repo, base_branch, slug, tool, router_profile, stage_since, owner_id) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
     )
     .run(
       normalizeTitle(title),
@@ -233,7 +234,8 @@ function createLane({
       slug,
       tool,
       router_profile || null,
-      nowIso()
+      nowIso(),
+      Number.isInteger(owner_id) ? owner_id : null
     );
   return getLane(info.lastInsertRowid);
 }