feat(intel): Telegram graph expansion to accounts interacting with monitored channels

## Problem
Described in specific detail to a prospect: "first we track specific Telegram
groups, then we extend from those by everybody that interacts with those
groups... you have to start from the centre and then go around them."

**No such code exists.** Ingestion is `scripts/ais-relay.cjs:924
loadTelegramChannels` over a fixed list in `data/telegram-channels.json`, whose
own `note` field reads: *"Product-managed curated list. Not user-configurable."*
There is no follower, commenter, or forwarder crawl anywhere in the repo.

## Why it matters
Telegram is a genuine differentiator — the founder's point that it beats X for
speed in conflict reporting is sound, and Dataminr also monitors Telegram
(confirmed via LAPD records). Graph expansion would be a real capability. Right
now it is a commitment.

## Considerations before building
- Telegram API rate limits and ToS on automated enumeration
- Storage and cost of an expanding channel set
- Trust scoring for auto-discovered channels — they should NOT inherit the seed
channel's tier (see the trust-registry issue)
- Moderation: auto-discovery will surface channels we do not want to ingest

## Acceptance
- [ ] Expansion from seed channels with an explicit depth limit
- [ ] Auto-discovered channels quarantined at lowest trust pending review
- [ ] Operator review queue before promotion
- [ ] Documented ToS position

Effort: L (~7d). Do not promise this again until it is built.

Start by reading scripts/ais-relay.cjs:924 loadTelegramChannels and data/telegram-channels.json to understand the current fixed seed-channel ingestion. Define the expansion boundary and review the listed rate-limit, storage, trust, moderation, and ToS considerations; done means depth-limited discovery, quarantined channels, an operator review queue, and documented ToS guidance.

Written by the indexing model from the issue text.