docs: privacy policy

[erfnzdeh]

Adds PRIVACY.md, links it from a short Privacy section in the README and from the plugin README, and sets privacyPolicyUrl in plugin/.claude-plugin/plugin.json so Anthropic's plugin directory shows it on the listing (it was one of the empty listing links).

What it states, each checked against the code:

• No collection. No telemetry, analytics, crash reporting or update checks. The only HTTP clients in tlgr/ are the webhook sender (daemon/webhook.py) and the mini-app download (ops/webapp.py); the daemon listens only on its Unix socket (web.UnixSite).
• Local storage. Everything under ~/.tlgr as named in core/paths.py: session files, API credentials, the peer cache, state, logs (allow-list redacted, core/logging.py), dead_letter.jsonl (can hold message text), downloads. Secret files are written 0600 (write_private).
• Outbound. Telegram (plus the device, system, app version and language strings from core/identity.py), the webhook if configured, an MTProto or SOCKS proxy if configured, and a mini-app file only on request.
• AI assistants. The plugin is instructions only; command output becomes part of the user's conversation with their AI provider, under that provider's policy.
• Age. Not intended for anyone under 18, matching the answer given in the directory submission.

Contact is GitHub issues, with SECURITY.md for private reports.