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

tauri/assets/talkbox.icon/icon.json

@@ -0,0 +1,29 @@
+{
+  "fill": "automatic",
+  "groups": [
+    {
+      "layers": [
+        {
+          "image-name": "TalkBox_Microphone.png",
+          "name": "TalkBox_Microphone",
+          "position": {
+            "scale": 0.36,
+            "translation-in-points": [0.140625, 270.1875]
+          }
+        }
+      ],
+      "shadow": {
+        "kind": "neutral",
+        "opacity": 0.5
+      },
+      "translucency": {
+        "enabled": true,
+        "value": 0.5
+      }
+    }
+  ],
+  "supported-platforms": {
+    "circles": ["watchOS"],
+    "squares": "shared"
+  }
+}