fix: batch A - crash bugs, a leak, and startup/edge fragility

Seven confirmed defects from the code audit, each small and low-risk.

* ai_functions.get_random_cyclic_message: random.randint(0, len(CYCLIC_WORDS))
  is inclusive -> could return len -> IndexError. Now randrange(len) + guard on
  an empty CYCLIC_WORDS.
* librarian_commands.get_image_sadox: random.randrange(0, len(res)-1) never
  picked the last comic and raised ValueError('empty range') on a single file.
  Now randrange(len) + an empty-dir guard.
* ai_commands image generation: every DALL-E error branch replied but did not
  return, so control fell through to `if response:` with response unbound ->
  UnboundLocalError right after the friendly message. Each branch now returns;
  response is pre-initialised; and PermissionDeniedError no longer passes a
  (message, text) tuple as a single arg.
* search_bot DOI match: `item["DOI"] in data` was a substring test, so a DOI
  that is a prefix of a longer one (10.1/1 vs 10.1/12) produced a false 'exists'
  hit. Now matches the line's first whitespace token exactly, via an O(1) dict
  index built once per consumer (also removes the O(queried-DOIs) per-line scan
  - a real win for large databases).
* communication_subroutine.scan_incoming: matched records were never removed
  from awaiting_q, so it grew unbounded over uptime and a reused UUID could
  re-match a stale record. Matched records are now dropped after dispatch.
* communication_subroutine.id3: (resp.headers.get("icy-name") or "").title()
  guards against a stream that omits headers (was AttributeError on None,
  500-ing the /prepped_tracks "next" handler).
* betoniarka.scan_tracks: waits for the radio logs to exist instead of dying
  with FileNotFoundError on a fresh deploy (which silently killed the
  now-playing forwarder until a restart).

Verified: tests/unit/test_search_bot.py gains exact-match and trailing-metadata
cases; full unit job 43 passed. Remaining observations (image-gen stale
/home/pi fallback paths + dead FileNotFoundError-after-OSError branch; tailer
still vulnerable to mid-run log rotation; DOI-first-token assumption) noted for
follow-up - none are crashes on the normal path.

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

ai_commands.py

@@ -427,6 +427,11 @@ class Events(commands.Cog):
                     return
                 message_content_lower = message_content_lower.replace("imaginuje sobie: ", "")
                 self.logger.debug("Wywolanie obrazka: %s", message_content_lower)
+                # Every error branch below must RETURN: otherwise control falls
+                # through to `if response:` with `response` unbound (the call
+                # raised) -> UnboundLocalError, crashing the handler right after
+                # the friendly message was already sent.
+                response = None
                 try:
                     response = await OPENAICLIENT.images.generate(
                         model="dall-e-3",
@@ -440,10 +445,12 @@ class Events(commands.Cog):
                     await discord_friendly_reply(
                         message, f"*Kondziu patrzy na terminal, czeka, czeka, czeka,.... Jeszcze chwile czeka Przypierdala w niego pięścią....* Nie mogę się połączyć z Openai spróbuj od nowa. *Na ekranie pojawia się*: {e}"
                     )
+                    return
                 except openai.APIConnectionError as e:
                     await discord_friendly_reply(
                         message, f"*Kondziu patrzy na terminal, chwile się zastanawia. Przypierdala w niego pięścią....* Nie mogę się połączyć z Openai. *Na ekranie pojawia się*: {e}"
                     )
+                    return
                 except openai.BadRequestError as e:
                     # Handle invalid request error, e.g. validate parameters or log
                     if message.author.nick:
@@ -461,27 +468,31 @@ class Events(commands.Cog):
                     await discord_friendly_reply(
                         message, f"Sorki, cenzura: {resp}. Jak chcesz to są kanały na nudle #sexy-foteczky i #kanal-do-fapania *Na ekranie pojawia się: {e}"
                     )
+                    return
                 except openai.AuthenticationError as e:
                     # Handle authentication error, e.g. check credentials or log
                     await discord_friendly_reply(
                         message, f"*Kondziu patrzy na terminal, chwile się zastanawia. Przypierdala w niego pięścią....* Wołaj szefa - coś się z hasłem zjebało. *Na terminalu pojawia się:* {e}"
                     )
+                    return
                 except openai.PermissionDeniedError as e:
                     # Handle permission error, e.g. check scope or log
+                    # (was accidentally passing a (message, text) TUPLE as one arg)
                     await discord_friendly_reply(
-                        (
-                            message, f"*Kondziu patrzy na terminal, chwile się zastanawia. Przypierdala w niego pięścią....* Wołaj szefa - coś się z uprawnieniami zjebało. *Na terminalu pojawia się:* {e}"
-                        )
+                        message, f"*Kondziu patrzy na terminal, chwile się zastanawia. Przypierdala w niego pięścią....* Wołaj szefa - coś się z uprawnieniami zjebało. *Na terminalu pojawia się:* {e}"
                     )
+                    return
                 except openai.RateLimitError as e:
                     await discord_friendly_reply(
                         message, f"*Kondziu patrzy na terminal* Wołaj szefa. Zapłacić rachunki za AI trzeba. Jak chcesz to się na #zebranie dorzuć. {e}"
                     )
+                    return
                 except openai.APIError as e:
                     # Handle API error, e.g. retry or log
                     await discord_friendly_reply(
                         message, f"*Kondziu nurkuje za bar, terminal wybucha. Przed tobą ląduje pergamin zapisany pięknym gotykiem a na nim*: {e}"
                     )
+                    return
                 if response:
                     self.logger.info(response)
                     image_url = response.data[0].url