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

docker-compose.rocm.yml

@@ -1,5 +1,5 @@
 ---
-# ROCm (AMD GPU) overlay for Voicebox
+# ROCm (AMD GPU) overlay for TalkBox
 #
 #   docker compose -f docker-compose.yml -f docker-compose.rocm.yml up --build
 #
@@ -8,7 +8,7 @@
 # RDNA4 (RX 9000): export ROCM_VERSION=7.2 (default 6.3 covers RDNA1-3).
 
 services:
-  voicebox:
+  talkbox:
     build:
       context: .
       args: