feat: Add complete async audio transcription workflow

Implemented full transcription system with local Whisper and OpenAI API
support. Includes comprehensive test suite (60 tests) and reorganized
keybindings for better discoverability.

Features:
- Async transcription (non-blocking workflow)
- Desktop notifications (started/complete/error)
- Output: audio.txt (transcript) + audio.log (process logs)
- Modeline integration showing active transcription count
- Dired integration (press T on audio files)
- Process management and tracking

Scripts:
- install-whisper.sh: Install Whisper via AUR or pip
- uninstall-whisper.sh: Clean removal with cache cleanup
- local-whisper: Offline transcription using installed Whisper
- oai-transcribe: Cloud transcription via OpenAI API

Tests (60 passing):
- Audio file detection (16 tests)
- Path generation logic (11 tests)
- Log cleanup behavior (5 tests)
- Duration formatting (9 tests)
- Active counter & modeline (11 tests)
- Integration workflows (8 tests)

Keybindings:
- Reorganized gcal to C-; g submenu (s/t/r/c)
- Added C-; t transcription submenu (t/b/k)
- Dired: T to transcribe file at point

1 files changed, 8 insertions, 0 deletions

diff --git a/modules/user-constants.el b/modules/user-constants.el
index ba52cec26..2a6d0ca2b 100644
--- a/modules/user-constants.el
+++ b/modules/user-constants.el
@@ -47,6 +47,14 @@ Example: (setq cj/debug-modules '(org-agenda mail))
   "Alist mapping buffer states to their colors.
 Used by cursor color, modeline, and other UI elements.")
 
+;; --------------------------- Media File Extensions ---------------------------
+
+(defvar cj/audio-file-extensions
+  '("m4a" "mp3" "wav" "flac" "ogg" "opus" "aac"
+    "aiff" "aif" "wma" "ape" "alac" "weba")
+  "File extensions recognized as audio files.
+Used by transcription module and other audio-related functionality.")
+
 ;; ------------------------ Directory And File Constants -----------------------
 
 ;; DIRECTORIES