Add build-your-own network to the roadmap

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/roadmap.md

@@ -92,6 +92,7 @@ Paul's ideas, 1 November 2026. Not fixes and not scheduled.
 - The highlighted left-menu item could reflect the channel or theme, while yellow stays the clear focus signal.
 - Orbit Drive-In gets its own full-screen destination, opened from the teaser card.
 - **Rings around the planet (Paul, 1 November 2026):** Orbit 1's background had its rings off to one side of the planet. The app's copy is fixed, from orbit-1/sources/orbit_1_background_v2.svg. Orbit 1's ident and the other channels built from the same planet layout (Orbit 2, Orbit Sci-Fi and any others on that theme) still need checking and the same fix before they join the app.
+- **Build your own network (Paul, 2 November 2026):** for anyone else using the app. On first sign-in, Orbit checks our channels against their library and ticks the ones it can fill, with those channels on by default. They can then edit any channel, adding or removing titles, turn channels on or off, and create new channels of their own. It's about people building what they want, as Paul did. In the pipeline, not scheduled.
 - **Seamless idents (Paul, 2 November 2026):** when idents arrive, the next show loads silently behind the ident and takes over as it ends, so there's no loading gap. To test: whether the box can decode two videos at once (otherwise draw the ident in the app), and a second Emby stream for a few seconds against the plan's limit of 3.
 - **Settings (Paul, 2 November 2026):** built in 0.72, then cut back in 0.73 to Channels, Watching and Emby account, as Paul wants only what's mandatory and a simple flow. The demo guide, old menu and test tools are gone.
 - **Subtitles default (Paul, 1 November 2026):** a setting behind the gear for subtitles on or off by default, in the viewer's language where a programme has it.