refactor(config): simplify to database-backed settings

- Reduce .env.example to only DATABASE_URL
- Simplify backend/config.py to only read database connection
- All other settings now managed via database and Web UI

.env.example

@@ -1,90 +1,20 @@
 # ============================================
 # TranscriptorIO Configuration
 # ============================================
+#
+# IMPORTANT: Most configuration is now stored in the database
+# and managed through the Web UI Settings page.
+#
+# Only DATABASE_URL is required in this file.
+# Run the server and complete the Setup Wizard for initial configuration.
+#
 
-# === Application Mode ===
-# Options: standalone, provider, or standalone,provider (hybrid mode)
-TRANSCRIPTARR_MODE=standalone
-
-# === Database Configuration ===
-# SQLite (default - no additional driver needed)
+# === Database Configuration (REQUIRED) ===
+# SQLite (default - good for single-user, no additional driver needed)
 DATABASE_URL=sqlite:///./transcriptarr.db
 
-# PostgreSQL example (requires psycopg2-binary)
+# PostgreSQL (recommended for production, requires psycopg2-binary)
 # DATABASE_URL=postgresql://user:password@localhost:5432/transcriptarr
 
-# MariaDB/MySQL example (requires pymysql)
+# MariaDB/MySQL (requires pymysql)
 # DATABASE_URL=mariadb+pymysql://user:password@localhost:3306/transcriptarr
-
-# === Worker Configuration ===
-CONCURRENT_TRANSCRIPTIONS=2
-WHISPER_THREADS=4
-TRANSCRIBE_DEVICE=cpu
-CLEAR_VRAM_ON_COMPLETE=True
-
-# === Whisper Model Configuration ===
-# Options: tiny, base, small, medium, large-v3, large-v3-turbo, etc.
-WHISPER_MODEL=medium
-MODEL_PATH=./models
-COMPUTE_TYPE=auto
-
-# === Standalone Mode Configuration ===
-# Pipe-separated paths to scan
-LIBRARY_PATHS=/media/anime|/media/movies
-AUTO_SCAN_ENABLED=False
-SCAN_INTERVAL_MINUTES=30
-
-# Filter rules for standalone mode
-REQUIRED_AUDIO_LANGUAGE=ja
-REQUIRED_MISSING_SUBTITLE=spa
-SKIP_IF_SUBTITLE_EXISTS=True
-
-# === Provider Mode Configuration ===
-BAZARR_URL=http://bazarr:6767
-BAZARR_API_KEY=your_api_key_here
-PROVIDER_TIMEOUT_SECONDS=600
-PROVIDER_CALLBACK_ENABLED=True
-PROVIDER_POLLING_INTERVAL=30
-
-# === API Configuration ===
-WEBHOOK_PORT=9000
-API_HOST=0.0.0.0
-DEBUG=True
-
-# === Transcription Settings ===
-# Options: transcribe, translate
-TRANSCRIBE_OR_TRANSLATE=transcribe
-SUBTITLE_LANGUAGE_NAME=
-# Options: ISO_639_1, ISO_639_2_T, ISO_639_2_B, NAME, NATIVE
-SUBTITLE_LANGUAGE_NAMING_TYPE=ISO_639_2_B
-WORD_LEVEL_HIGHLIGHT=False
-CUSTOM_REGROUP=cm_sl=84_sl=42++++++1
-
-# === Skip Configuration ===
-SKIP_IF_EXTERNAL_SUBTITLES_EXIST=False
-SKIP_IF_TARGET_SUBTITLES_EXIST=True
-SKIP_IF_INTERNAL_SUBTITLES_LANGUAGE=eng
-# Pipe-separated language codes
-SKIP_SUBTITLE_LANGUAGES=
-SKIP_IF_AUDIO_LANGUAGES=
-SKIP_UNKNOWN_LANGUAGE=False
-SKIP_ONLY_SUBGEN_SUBTITLES=False
-
-# === Advanced Settings ===
-FORCE_DETECTED_LANGUAGE_TO=
-DETECT_LANGUAGE_LENGTH=30
-DETECT_LANGUAGE_OFFSET=0
-SHOULD_WHISPER_DETECT_AUDIO_LANGUAGE=False
-# Pipe-separated list in order of preference
-PREFERRED_AUDIO_LANGUAGES=eng
-
-# === Path Mapping ===
-USE_PATH_MAPPING=False
-PATH_MAPPING_FROM=/tv
-PATH_MAPPING_TO=/Volumes/TV
-
-# === Legacy SubGen Compatibility ===
-SHOW_IN_SUBNAME_SUBGEN=True
-SHOW_IN_SUBNAME_MODEL=True
-APPEND=False
-LRC_FOR_AUDIO_FILES=True