feat(train): the instance names its map source (ADR 0030, D11, D22)

Train's first endpoint of its own, map.source, names the map workouts
are drawn on, for people signed in only, as a provider's key may be in
its style's address: OpenFreeMap's Liberty style where the operator sets
nothing, else MAP_STYLE_URL (HTTPS only) with MAP_SOURCE_NAME,
MAP_ATTRIBUTION and MAP_ABOUT_URL. A model without a table: no
migration. D22 is recorded in ADR 0030.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0030-halkyon-train.md

@@ -1,7 +1,7 @@
 # ADR 0030: Halkyon Train, what it does and where its data comes from
 
-- **Status:** decided 27–28 Oct 2026, by the developer (D1–D21 below). The shell (D12)
-  is built; recording (D13–D21) is being built.
+- **Status:** decided 27–28 Oct 2026, by the developer (D1–D22 below). The shell (D12)
+  is built; recording (D13–D22) is being built.
 - **Numbering:** 0025 is held by the federation draft (stashed), 0026–0029 by the .NET
   rewrite on the local branch `rewrite-dotnet`, abandoned on 27 Oct; Train takes the next
   free number so that neither is ever read as this one.
@@ -337,6 +337,16 @@ Strava. What was found, 27 Oct:
   than in a snack bar, which would cover the button it speaks of. The service holds a
   partial wake lock while it records (at most 12 hours), so that its clock and file run
   with the screen off where no GPS fix wakes the processor.
+- **D22 OpenFreeMap first, the PMTiles sidecar with route planning** (recommended, over
+  the sidecar now, which no one else ever sees the areas viewed through but needs Train's
+  server and the sidecar deployed on learn.halkyon.eu before anything else of Train is
+  ready, and a region chosen, gigabytes on the server's disk; and over a source fixed in
+  the app, which skips D11's operator's setting and would be undone): Train's server names
+  the instance's map source, as its operator sets it, OpenFreeMap where nothing is set
+  (D11), so 5c needs no deploy; a workout's page names the source drawing it and what it
+  sees (the device's address and the area viewed, not the track). The sidecar comes when
+  route planning gives Train's server a reason to run on the instance: the region's
+  PMTiles file served by Caddy with range requests, no server code.
 
 ## Consequences