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

landing/README.md

@@ -1,6 +1,6 @@
-# Voicebox Landing Page
+# TalkBox Landing Page
 
-Landing page for voicebox.sh - a modern Next.js 16 application.
+Landing page for talkbox.sh - a modern Next.js 16 application.
 
 ## Tech Stack
 
@@ -65,7 +65,7 @@ Replace `USERNAME` in `src/lib/constants.ts` with your actual GitHub username.
    - Install dependencies with `bun install`
    - Build with `bun run build`
    - Start with `bun run start`
-5. Configure custom domain `voicebox.sh` in Railway settings
+5. Configure custom domain `talkbox.sh` in Railway settings
 
 ## Project Structure
 
@@ -85,7 +85,7 @@ landing/
 │       ├── utils.ts        # Utility functions
 │       └── constants.ts    # App constants
 ├── public/
-│   └── voicebox-logo.png   # Logo asset
+│   └── talkbox-logo.png   # Logo asset
 └── nixpacks.toml          # Railway deployment config
 ```