SafeDrop v1.6.0

The "actually finish v1.6 + introduce the project" release. Closes
out the cross-platform native rendering of v1.6 primitives and ships
the docs needed to onboard new users / contributors.

Added — native notification rendering on all 3 platforms

• Python tkinter banner for inbound show_notification. gui.py
  subscribes to safedrop.notifications.bus.on_notification and pops
  a transient Toplevel (auto-dismiss after 8 s, color-coded by
  info/warn/error).
• iOS UNUserNotificationCenter — new show_notification handler
  in ios/SafeDrop/Tools.swift drops a system banner via
  UNTimeIntervalNotificationTrigger. App requests .alert + .sound
  authorization on launch.
• Android NotificationManager — new show_notification handler
  in android/.../net/ToolRegistry.kt posts via
  NotificationCompat.Builder with a lazy-created channel. Added
  POST_NOTIFICATIONS permission to AndroidManifest and runtime
  request via ActivityResultContracts.RequestPermission in
  MainActivity for API 33+.
• Moved notification_tools.py from safedrop_mcp/ to
  safedrop/notifications.py so the desktop GUI can use it without
  the [mcp] extra installed. MCP server imports updated.

Added — iOS token management UI

• New ios/SafeDrop/TokenAdminView.swift — SwiftUI screen that calls
  the cross-device peer tools (tokens_list, tokens_mint,
  tokens_revoke) on a selected SafeDrop peer (the desktop running
  safedrop-mcp). Mint form with label / scope / TTL fields;
  one-time secret reveal sheet on success.
• Toolbar key icon in HomeView opens TokenAdminView when the
  selected peer advertises safedrop.tools.

Added — introducing the project

• docs/landing.html — single-page self-contained landing page
  (no external deps, dark theme, hero + features + architecture
  diagram + install snippet + cross-platform capability matrix +
  security model + roadmap). The thing you link from a README badge.
• docs/pitch.md — 30-second + 2-minute pitches for a HN post /
  Twitter thread.
• docs/demo-recipes.md — six tight live-demo recipes (each
  ~30-90 s), with exact commands + audience-facing punchline. Covers
  cross-platform AirDrop, agent-with-phone-camera, two-agent mesh,
  state handoff, mobile token mint, and Tailscale cross-LAN.

Changed

• pyproject.toml → 1.6.0.