Torrent / IPFS / magnet URI bridging

[MudDev]

Spun out from #10 (point 8, raised by @mx5kevin).

Problem

EpixNet today is a closed P2P swarm. Files available on EpixNet aren't reachable from BitTorrent/IPFS clients and vice versa, which:

• Forces users to run EpixNet as a separate program alongside their existing download tools
• Makes it harder to seed the same large files across networks without duplicating storage
• Limits discoverability of EpixNet content

AnnounceBitTorrent announces to BitTorrent trackers for peer discovery, but does not bridge the protocols themselves.

Proposal

Explore protocol bridging in three directions:

1. Magnet URI / torrent import

• Let a site reference an external magnet URI or torrent infohash
• EpixNet client downloads the file via BT and serves it via EpixNet's push swarm
• Single reference, shared across sites (composes with Add default optional-file pattern to content.json-default #11 cross-site dedup)

2. IPFS CID references

• Sites can reference IPFS CIDs for large/immutable content
• EpixNet client fetches via IPFS gateway or embedded node
• Optional: publish EpixNet files to IPFS for wider availability

3. Outbound torrent seeding

• Files hosted on EpixNet can be made available as torrents
• Uses existing hashfield + push swarm as the seeder backend

Design questions

• Bundle a BT client (libtorrent) or shell out to external client?
• How do infohash -> content.json references get signed/verified?
• What's the trust model when pulling from external networks?
• Per-site opt-in or global?

Non-goals

• Not replacing EpixNet's native swarm, this is additive
• Not claiming feature parity with dedicated BT clients

Credit: @mx5kevin in #10.