feat: split settings DB from the QSO logbook (own file per profile)

Design flaw: opslog.db held BOTH the config (settings + profiles) AND the SQLite
logbook, so the only way to a separate SQLite logbook — the whole-app "change
database location" pointer — swapped the config too, wiping the operator's setup
(reported: creating a new SQLite for a visiting op lost all profiles/settings).

Now the two are separate files:
- Settings database: settings + profiles. Fresh installs name it settings.db;
  existing installs keep opslog.db.
- Logbook (QSOs): a dedicated logbook.db next to the settings db, or a
  per-profile file (profile.ProfileDB.Path), or MySQL. connectLogbook opens the
  logbook file (db.Open creates+migrates on first use); the settings db is used
  as the logbook only if the split ever fails.

One-time, non-destructive migration at startup: if there's no logbook file yet
but the settings db already holds QSOs (legacy combined opslog.db), seed
logbook.db with a clean copy via VACUUM INTO — contacts move to the logbook, the
originals stay in the settings db as an untouched backup.

UI: the Database panel now shows the settings database and this profile's logbook
as two clearly labelled sections (+ "Open folder"), and the logbook selector is
SQLite (default logbook.db, or a dedicated file via "Choose a dedicated file…")
vs MySQL — no more confusing shared/separate choice. New binding RevealDataFolder.

frontend/wailsjs/go/main/App.d.ts

@@ -764,6 +764,8 @@ export function RestartQSORecorder():Promise<void>;
 
 export function RetryOfflineSync():Promise<number>;
 
+export function RevealDataFolder():Promise<void>;
+
 export function RotatorGoTo(arg1:number,arg2:number):Promise<void>;
 
 export function RotatorPark():Promise<void>;

frontend/wailsjs/go/main/App.js

@@ -1482,6 +1482,10 @@ export function RetryOfflineSync() {
   return window['go']['main']['App']['RetryOfflineSync']();
 }
 
+export function RevealDataFolder() {
+  return window['go']['main']['App']['RevealDataFolder']();
+}
+
 export function RotatorGoTo(arg1, arg2) {
   return window['go']['main']['App']['RotatorGoTo'](arg1, arg2);
 }