TTS: configurable auth, Health check, Phoenix options; .env.example; Gitea CI workflow

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

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+# Virtual Banker — example environment (copy to .env and set values)
+# Do not commit .env; use secrets in CI/production.
+
+# Database and Redis
+DATABASE_URL=postgres://user:pass@localhost:5432/virtual_banker?sslmode=disable
+REDIS_URL=redis://localhost:6379
+PORT=8081
+
+# TTS: ElevenLabs (default) or Phoenix
+# Leave unset to use mock TTS. Set TTS_VOICE_ID + one of the keys for real TTS.
+TTS_VOICE_ID=
+TTS_API_KEY=
+# ELEVENLABS_API_KEY=   # alternative to TTS_API_KEY
+# ELEVENLABS_VOICE_ID=  # alternative to TTS_VOICE_ID
+
+# Phoenix / custom TTS endpoint (optional)
+# TTS_BASE_URL=https://phoenix.example.com/tts/v1
+# TTS_AUTH_HEADER_NAME=Authorization
+# TTS_AUTH_HEADER_VALUE=Bearer your-token
+# USE_PHOENIX_TTS=true
+# PHOENIX_TTS_BASE_URL=https://phoenix.example.com/tts/v1