feat: connect-scripts + opt-in route gossip

[M0LTE]

Summary

Two composing changes:

Connect-scripts automate the operator's manual `C nodeA / C nodeB / DAPPS` chain for reaching a far-end DAPPS peer through a chain of bare packet nodes that don't speak DAPPS or NET/ROM. Script lives on the neighbour row as a list of (send, expect) steps; the daemon plays it before falling into the DAPPSv1 prompt. Used by forwarder, probe, and poll paths.

Route gossip piggybacks a new `routes` command on otherwise-open sessions (push / probe / poll), bounded by a per-(local, remote) staleness gate. Imported routes land in `learnedroutes` with `Source="gossip"`; existing failure-counter machinery handles invalidation. Advertiser filter suppresses unproven routes and never re-exports hearsay (avoids distance-vector loops).

These compose: a connect-script unblocks the cold-start case A→C through bare nodes; gossip then propagates further-reach destinations beyond the manually configured pair.

What's new

• `DAPPSv1` gains the `routes` verb. Wire form: `route hops=N ageSeconds=N` per line, `end` terminator. Forward-compatible (unknown KVs ignored).
• `DbNeighbour.ConnectScriptJson` + `DbLearnedRoute.Source` + `DbRouteGossipState` schema additions.
• `SystemOptions.RouteGossipStalenessHours` (default 6, 0 disables gossip entirely).
• Dashboard Neighbours panel: connect-script textarea on the add/update form, step-count column on the listing.
• New docs: `docs/multi-hop.md` covers the through-non-DAPPS-intermediates scenario end-to-end. `implement.md` extended with the `routes` verb. `discovery-and-routing.md` gains a Route gossip section.

Test plan

• `dotnet build` clean across all projects (dapps.client, dapps.core, dapps.core.tests, harness, uitests, FakeBpqAndDappsClient)
• `dotnet test`: 584 / 584 passing (565 baseline + 19 new across ConnectScriptTests + RouteGossipTests)
• `mkdocs build --strict` clean
• Connect-script: parse round-trip text↔JSON; runner happy-path drives a fake duplex stream and observes substring matches; timeout fires when peer is silent; EOF mid-script throws cleanly; substring matching works across read boundaries
• Route gossip: staleness gate (never-pulled allows; recent blocks; elapsed re-allows; staleness=0 always blocks); gossip upsert respects traffic priority (won't downgrade a traffic-learned row); rejects self-routes (advertiser advertising themselves); gossip-replaces-gossip resets failure counter on next-hop change
• Existing routing-algorithm sites (Static, PassiveLearning, FloodFallback, MeshCoreLike) all use the new `RouteBuilder.FromNeighbour` helper so connect-scripts flow through every code path
• Probe and poll scheduler services pass connect-scripts to NodeProber/NodePoller when the neighbour has one configured
• Backwards-compatible: existing neighbours with no script behave exactly as before; daemons that don't implement `routes` return `eh?` and senders treat that as "stop trying"

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