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

SECURITY.md

@@ -14,7 +14,7 @@ We release patches for security vulnerabilities. Which versions are eligible for
 If you discover a security vulnerability, please report it responsibly:
 
 1. **Do not** open a public GitHub issue
-2. Email security details to: [security@voicebox.sh](mailto:security@voicebox.sh)
+2. Email security details to: [security@talkbox.sh](mailto:security@talkbox.sh)
 3. Include:
    - Description of the vulnerability
    - Steps to reproduce
@@ -31,7 +31,7 @@ We will:
 
 ### For Users
 
-- **Keep Voicebox updated** - Updates include security patches
+- **Keep TalkBox updated** - Updates include security patches
 - **Verify downloads** - Only download from official releases
 - **Local processing** - Voice data stays on your machine
 - **Network security** - Use HTTPS when connecting to remote servers
@@ -47,7 +47,7 @@ We will:
 
 ### Local Processing
 
-Voicebox processes all audio locally by default. Your voice data never leaves your machine unless you explicitly enable remote server mode.
+TalkBox processes all audio locally by default. Your voice data never leaves your machine unless you explicitly enable remote server mode.
 
 ### Remote Server Mode
 
@@ -89,4 +89,4 @@ Security updates will be:
 
 ---
 
-Thank you for helping keep Voicebox secure! 🔒
+Thank you for helping keep TalkBox secure! 🔒