Merge master, dedupe the kept copy, and retire superseded switches

Master had moved ten commits ahead. Two conflicts, both resolved without
losing either side: the `XTREAM_PROBE_URL` handler this PR extracted into
`events/stream-probe.ts` stays extracted (master added performance capture
nearby but never touched that handler), and the mock-server scenario table
takes the union of master's `performance` row and this branch's `multisrc`
pair.

Two findings fixed alongside it.

Pinning the copy the route is already on makes discovery return that very
row, so prepending the current source listed one stream twice — a phantom
copy in the grouping and a chip that counted it.

And handing the "playing" badge back to the route row left an in-flight
switch valid, so a slow resolution could arrive afterwards and replace the
playback the user had just started with Play, Resume or Restart.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.changes/electron-backend-zero-delay-cancellation.md

@@ -0,0 +1,8 @@
+---
+type: fix
+area: electron-backend
+---
+
+Cancelling a large Xtream import now stops database work even while it is
+running at full speed, instead of letting the import finish before processing
+the cancel request.

.changes/epg-mapping-fail-soft.md

@@ -0,0 +1,9 @@
+---
+type: fix
+area: epg
+---
+
+A database error while looking up manual EPG channel mappings no longer breaks
+the request that triggered it. Searching for a channel in the "Map EPG channel"
+dialog, or saving and removing a mapping, now degrades gracefully instead of
+failing outright.

.changes/epg-mapping-lookup-fail-soft.md

@@ -0,0 +1,9 @@
+---
+type: fix
+area: epg
+---
+
+A database error while reading or saving a manual EPG channel mapping no longer
+surfaces as a failed request. Looking up, saving, deleting, and searching
+mappings now fall back quietly, so a transient storage hiccup can no longer take
+down the EPG panel or the "Map EPG channel" dialog.

.changes/settings-persistence-feedback.md

@@ -0,0 +1,10 @@
+---
+type: fix
+area: settings
+issues: [1156, 102]
+---
+
+Launching IPTVnator a second time now brings the running window to the front
+instead of starting a rival copy that could not save anything — a common reason
+settings appeared to reset on restart. If saving or loading settings does fail,
+the app now says so instead of silently showing defaults.