fix: remove tauri-plugin-log to avoid logger conflict

`tracing_subscriber::fmt().try_init()` installs a global log
implementation via the tracing-log shim. tauri-plugin-log then
calls `log::set_logger()` which panics with "attempted to set a
logger after the logging system was already initialized".

The plugin was never wired in JS code (no @tauri-apps/plugin-log
import) — backend logging via tracing is sufficient. Drop:
  - tauri-plugin-log dep + plugin registration
  - log:default capability permission
  - @tauri-apps/plugin-log JS dep

Verified: cargo check is clean, app starts past the panic.

src-tauri/capabilities/default.json

@@ -6,7 +6,6 @@
   "permissions": [
     "core:default",
     "store:default",
-    "log:default",
     "dialog:default"
   ]
 }