feat(epg): add global EPG display time offset (#1489)

Adds a global EPG display-time offset (Settings → EPG, whole minutes, ±720) for guides whose provider labels programme times with the wrong timezone. Display-only: parsed XMLTV values, SQLite rows, catch-up URLs and recording snapshots keep the provider's own times, so changing it needs no guide refresh. Closes the global part of #50.

The contract lives in `libs/shared/interfaces/src/lib/epg-display-offset.util.ts` with two equivalent forms: `epgDisplayTimeMs` shifts a programme for display, `epgProviderClockMs` shifts "now" into the provider's clock for every "currently airing" decision — the batched `GET_CURRENT_PROGRAMS_BATCH` lookup takes an explicit `nowMs`, and the channel lists, the Xtream/Stalker previews, the M3U player's current-programme mirror, the unified collection resolver, the dashboard live cards and the recording overlap all pick the same programme the guide renders as "now". Portal short-EPG windows start at the provider's own "now", so under a non-zero offset the Xtream preview surfaces cut their window from the full guide at the provider clock, Stalker short-EPG requests are widened for negative offsets, and every per-stream memory of the previous offset is retired together when the setting changes.

Co-authored-by: Mark Jardine <markjardine27@gmail.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

libs/shared/interfaces/src/lib/electron-api.interface.ts

@@ -362,6 +362,19 @@ export interface ElectronBridgeEpgLookupOptions {
     sourceUrls?: string[];
 }
 
+/**
+ * Options for the batched "currently airing" lookup. `nowMs` is the instant
+ * the lookup is evaluated at: the renderer passes its wall clock shifted into
+ * the provider's EPG clock (`epgProviderClockMs`, see
+ * `epg-display-offset.util.ts`) so the row the backend picks is the one the
+ * renderer will also present as "now". Absent, the main process uses its own
+ * clock.
+ */
+export interface ElectronBridgeCurrentProgramsOptions
+    extends ElectronBridgeEpgLookupOptions {
+    nowMs?: number;
+}
+
 export interface ElectronBridgeEpgProgressStats {
     totalChannels: number;
     totalPrograms: number;
@@ -778,7 +791,7 @@ export interface ElectronBridgeApi {
     ) => Promise<EpgProgram[]>;
     getCurrentProgramsBatch: (
         channelIds: string[],
-        options?: ElectronBridgeEpgLookupOptions
+        options?: ElectronBridgeCurrentProgramsOptions
     ) => Promise<Record<string, EpgProgram | null>>;
     getEpgChannelMetadata: (
         channelIds: string[],