rebrand: rename VoiceBox to TalkBox throughout codebase

- All 'voicebox'/'Voicebox'/'VOICEBOX' strings replaced with 'talkbox'/'TalkBox'/'TALKBOX'
- Port changed from 17493 to 17494 (avoids conflict with upstream VoiceBox)
- MCP tool namespace: voicebox.* -> talkbox.*
- App bundle ID: sh.voicebox.app -> com.talkbox.app
- Binary names: voicebox-server -> talkbox-server, voicebox-mcp -> talkbox-mcp
- Docker user/group: voicebox -> talkbox
- Database: voicebox.db -> talkbox.db
- Env vars: VOICEBOX_* -> TALKBOX_*
- Asset files renamed: voicebox-logo.* -> talkbox-logo.*, etc.
- External binaries in tauri.conf.json updated to talkbox-server/talkbox-mcp

backend/routes/profiles.py

@@ -294,7 +294,7 @@ async def export_profile(
         safe_name = "".join(c for c in profile.name if c.isalnum() or c in (" ", "-", "_")).strip()
         if not safe_name:
             safe_name = "profile"
-        filename = f"profile-{safe_name}.voicebox.zip"
+        filename = f"profile-{safe_name}.talkbox.zip"
 
         return StreamingResponse(
             io.BytesIO(zip_bytes),