feat: right-click menus everywhere, workspace/session cost, long-term DB safety

Right-click menus: one portal shell (components/ContextMenu.tsx) for every
item with actions - sidebar/Recents/archived session rows (SessionMenu),
console tabs, pane headers, the Changes panel's files/tree/commits, the
workspace home, sessions outside a workspace (SessionRowMenu: Sessions
table, Dashboard, Activity, Workflow runs), prompt images, every Settings
list and every Claude Code/Codex config list (FileItemMenu). Buttons stay;
a delete keeps its button's confirm; the shell stops portal clicks from
reaching the card that opened it.

Status bar: Workspace $ and Session $ on the Workspace page, from
?lane= on GET /api/pricing/cost and the focused/replayed session's cost.

Database, no data dropped: synchronous=NORMAL, journal_size_limit 64 MB,
hourly PASSIVE checkpoint + PRAGMA optimize, idx_events_session_created
(replacing the redundant idx_events_session), watchdog reads
sessions.transcript_path, transcript parsed before the hook's write
transaction, GET /api/sessions/:id?events=0 for the web page (reloads only
on its own session, debounced), streamed export, transactional clear-data
and chunked cleanup, subagent import reads tool_use_ids once, runtime logs
rotated past 5 MB.

.env.example

@@ -71,6 +71,10 @@
 # Set to 0 to disable the poll while leaving the watcher running (default: 30000).
 #   DASHBOARD_SESSION_SYNC_MS=30000
 
+# Hourly database upkeep: a non-blocking WAL checkpoint (the WAL then shrinks
+# to 64 MB) and PRAGMA optimize. 0 turns it off. Never VACUUMs.
+#   DASHBOARD_DB_MAINTAIN_MS=3600000
+
 # Poll interval (ms) for Antigravity CLI sessions and tokens, read from agy's
 # own ~/.gemini/antigravity-cli/conversations/*.db (0 disables; default: 15000).
 #   DASHBOARD_ANTIGRAVITY_POLL_MS=15000