feat(dht): Phase 4 — paid swarm streaming (cross-mint ecash + Shape-A ALPN)

Fetch-side auto-pay decision layer (payment.rs), Shape-A paid-blobs
negotiation ALPN (paid_alpn.rs), cross-mint ecash swap + payer auto-swap
builder + idempotent resume/liquidity cache (ecash.rs), and the
streaming.prepare-payment RPC. All gated behind the iroh-swarm feature
(off by default). 91/91 tests pass, both build configs clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/phase4-streaming-ecash-plan.md

@@ -321,6 +321,15 @@ blobs flow peer-to-peer with MinIO/OVH as origin.
 A→E delivers "films on every node" with free volunteer seeding (the design-doc
 vision). F→H layer the sats economy on top. I is genuinely future work.
 
+> **Shipping directive (user, 2026-06-17):** the IndeeHub "Archipelago" change
+> ships — after testing — as a **decoupled app-catalog update**, NOT a binary
+> OTA. Publish the new IndeeHub image + bump `releases/app-catalog.json` so every
+> node gets the per-app "Update" badge (the mechanism in
+> `container/app_catalog.rs` / `package.check-updates`). Node-side API changes
+> (steps B/C) that need the binary go through the normal OTA; the *app* (step D,
+> the IndeeHub frontend image) goes through the app catalog. See memories
+> `project_decoupled_app_updates` + `reference_indeehub_canonical_source`.
+
 ---
 
 ## 5. Open questions / decisions needed