librarian: mount + seed runtime JSON state under /lib_temp_files

(Re-applied cleanly on top of main: PR #18 was rebase-merged, so the branch
that became #19 conflicted on the already-landed commits. This carries ONLY
the librarian state fix - the sole content difference between that branch
and main - so nothing else is touched or lost.)

The worker threads open cr_results/rr_results/not_in_db/s_results.json in
place ('r+'), crashing with FileNotFoundError in a fresh container. New
conjurer_librarian/lib_paths.py resolves all four under a persistent dir
(CONJURER_LIBRARIAN_STATE_DIR, default /lib_temp_files) and seeds missing
ones with '{}' on import; shared by conjurer_librarian.py and scrape_bot.py
(no circular import). ndb_database/database initialised to {} before load so
a corrupt persisted file degrades to empty instead of NameError. search_bot
/search_bot2 open the DOI DB 'r' not 'r+' so /doi can stay read-only. Docker:
STATE_DIR env + VOLUME, compose mounts /srv/librarian/state:/lib_temp_files.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

conjurer_librarian/search_bot.py

@@ -47,7 +47,7 @@ def producer(out_q, control_q, filename, _logger):
         filename (str): Name of the file.
         _logger: Logger object for logging.
     """
-    with open(DATABASE_PATH + filename, "r+", encoding=ENCODING) as operated_file:
+    with open(DATABASE_PATH + filename, "r", encoding=ENCODING) as operated_file:
         print(f"Worker {filename} ")
         line_no = 0
         while True: