Desktop GUI: Library tab with live sync to the server

- new Record/Library tabs (like the mobile app); the recording UI is
  unchanged inside the Record tab
- Library tab: recording list (date, duration, language, device), detail
  view with summary (scrollable, re-triggerable), agenda checklist with
  coverage marks, and the full timestamped transcript; Library URL field
  (defaults to MEETREC_LIBRARY_URL)
- sync: auto-refresh every 10 s — recordings made on the phone appear on
  the desktop while the tab is open; pending summaries update to done
  automatically and re-fetch
- shared library client in meetrec.py: library_list/library_get_file/
  library_trigger_summary
- validated headlessly (offscreen) against the live server: 6 recordings
  from phone and desktop listed, 68-min meeting detail with 1333-char
  summary and ~100k-char transcript

README.md

@@ -157,6 +157,19 @@ MEETREC_DIARIZE_URL=http://100.103.83.12:8086 \
 - `--agenda-file` supplies the agenda items (one per line).
 - `--diarize-url` adds a second tinydiarize pass whose speaker-turn times are merged onto the transcript as `Sprecher 1:/Sprecher 2:` labels (2 speakers, best-effort on non-English audio; failures keep the transcript unlabeled).
 - The GUI has the same options as fields (Library URL, Diarize URL, agenda editor).
+
+## Library tab (GUI)
+
+The desktop GUI has **Record** and **Library** tabs like the mobile app. The
+Library tab browses the server's recordings with summary, agenda coverage
+and the full transcript, and **auto-refreshes every 10 s** — record on the
+phone, and the meeting appears on the desktop while the tab is open:
+
+```sh
+MEETREC_LIBRARY_URL=http://100.103.83.12:8090 python meetrec_gui.py
+```
+
+(The URL can also be typed into the tab's Library URL field.)
 - `--device` / `--compute-type` do not apply (GPU vs. CPU is decided by the whisper.cpp build).
 
 ## Project layout