Dispatcharr Phase 1: native API source loading

[kristofferR]

Part of #200. Fully shippable on its own (load + scan Dispatcharr source streams, read-only).

New src-tauri/src/engine/dispatcharr.rs (register in engine/mod.rs)

• DispatcharrClient — normalize base URL like normalize_xtream_server (playlist.rs:775); reqwest client with the same knobs as the playlist downloader. ensure_token(): API-key header if set, else JWT login → cache access token (expiry now+25 min) → refresh on expiry → full re-login on 401; request() retries once on 401.
• Serde-tolerant DTOs: DispatcharrChannel { id, uuid, channel_number, name, channel_group, tvg_id, logo, streams }, DispatcharrStream { id, name, url, m3u_account, is_custom, tvg_id, is_stale, stream_stats, ... }, DispatcharrGroup.
• fetch_all<T>() handling both bare arrays and DRF {count, next, results} pagination (untagged enum), rewriting next host onto the base URL (reverse-proxy gotcha), hard page ceiling (500). Fetchers: channels, per-channel streams, groups, m3u accounts (accounts tolerate failure).
• build_m3u(...): one #EXTINF per stream; name = channel name, or "{name} [{order+1}/{count}] {account-or-stream-name}" for multi-stream channels; attrs tvg-id, tvg-chno, tvg-logo ({base}/api/channels/logos/{id}/cache/), group-title, plus the five x-dispatcharr-* attrs (escape quotes). URL line = provider stream.url.
• dispatcharr_ids_from_extinf(&str) -> Option<DispatcharrStreamRef> built on parse_extinf_attributes.
• Session registry: register_session(identity, Arc<DispatcharrClient>) / get_session(identity) (same pattern as SERVER_LOCATION_CACHE).
• Write-op signatures used later by Dispatcharr Phase 2: scan source streams #202: patch_stream_stats, set_channel_streams, bulk_delete_streams.

Modified src-tauri/src/commands/playlist.rs

• DispatcharrOpenRequest { server, username, password, api_key } (next to XtreamOpenRequest).
• open_playlist_dispatcharr + _inner mirroring open_playlist_xtream_inner: validate (api_key OR user+pass) → source key dispatcharr:{host}|{user} (mirror build_xtream_source_key) → emit playlist://load-progress stages → fetch channels/groups/accounts via tokio::join!, per-channel streams with buffer_unordered(8) → build_m3u → write_bytes_to_cache → parse_playlist_with_progress → set preview.file_name = "{host} (Dispatcharr)" and preview.source_identity → register_session.

Saved/recent/wiring

• SavedPlaylistSource::Dispatcharr { server, username?, password?, api_key? } variant + SavedPlaylistKind arm (models/saved_playlist.rs); arms in commands/saved.rs (default_display_name, sanitize_saved_playlist_entry, open_saved_playlist with identity override saved:{id}); RecentPlaylistKind::Dispatcharr in commands/recent.rs (secrets only if "remember" checked); register the command in lib.rs invoke_handler.

Frontend

• src/lib/types.ts + src/lib/tauri.ts: request type + openPlaylistDispatcharr wrapper.
• src/components/OpenSourceDialog.tsx: new "Dispatcharr" tab (server URL, API-key vs username/password toggle, remember-credentials); autofill server from pasted /proxy/ts/stream/ or /output/m3u URLs (mirror parseXtreamM3ULink).
• src/App.tsx: openPlaylistDispatcharrValue callback modeled on openPlaylistXtreamValue.
• SavedPlaylistEditorDialog.tsx + src/lib/savedPlaylists.ts: dispatcharr form branch.

Tests

• engine/dispatcharr.rs unit tests using the spawn_http_server pattern from checker.rs, extended to capture method+body: JWT login/refresh/401-retry, API-key header, pagination (paginated + bare array + host rewrite).
• Pure tests: build_m3u → parser::parse_m3u → dispatcharr_ids_from_extinf round-trip (the load-bearing invariant); attr escaping.
• SavedPlaylistSource::Dispatcharr serde round-trip; legacy JSON still parses.