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/history.py

@@ -153,7 +153,7 @@ async def export_generation(
         safe_text = "generation"
     # Append a short id so exports of similarly-worded generations don't collide
     # on the same filename (the first 30 chars are frequently identical).
-    filename = f"generation-{safe_text}-{generation_id[:8]}.voicebox.zip"
+    filename = f"generation-{safe_text}-{generation_id[:8]}.talkbox.zip"
 
     return StreamingResponse(
         io.BytesIO(zip_bytes),