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/mcp_shim/__init__.py

@@ -1,10 +1,10 @@
-"""Stdio → Streamable HTTP bridge for the Voicebox MCP server.
+"""Stdio → Streamable HTTP bridge for the TalkBox MCP server.
 
 Some MCP clients only know how to spawn a subprocess and talk to it over
 stdin/stdout (the "stdio" transport). This package is a ~150-line adapter:
-the client spawns us as ``voicebox-mcp``; we proxy every JSON-RPC frame
-to http://127.0.0.1:17493/mcp/ and stream responses back out.
+the client spawns us as ``talkbox-mcp``; we proxy every JSON-RPC frame
+to http://127.0.0.1:17494/mcp/ and stream responses back out.
 
-All the real work (tools, models, inference) lives in the Voicebox server
+All the real work (tools, models, inference) lives in the TalkBox server
 process — this package contains no business logic.
 """