feat: rename the database from Settings, keeping all config

Adds a Rename button to Settings -> Database: renames the current SQLite database
(e.g. opslog.db -> F4BPO.db) while preserving every setting/profile, unlike New
database which starts empty. Implemented as a VACUUM INTO copy + pointer switch;
the old file (open and locked now) is scheduled via config.json delete_pending
and removed, with its -wal/-shm sidecars, on the next launch.

app.go

@@ -699,6 +699,20 @@ func (a *App) startup(ctx context.Context) {
 			usingDefault = false
 		}
 	}
+	// A rename in a previous session left the OLD file to delete now that it's no
+	// longer open. Only ever delete a file that ISN'T the one we're about to use.
+	if boot := readBootstrap(dataDir); strings.TrimSpace(boot.DeletePending) != "" {
+		old := strings.TrimSpace(boot.DeletePending)
+		if old != a.dbPath {
+			for _, p := range []string{old, old + "-wal", old + "-shm"} {
+				if err := os.Remove(p); err == nil {
+					fmt.Printf("OpsLog: removed old database file %s\n", p)
+				}
+			}
+		}
+		boot.DeletePending = ""
+		_ = writeBootstrap(dataDir, boot)
+	}
 	if err := os.MkdirAll(filepath.Dir(a.dbPath), 0o755); err != nil {
 		a.startupErr = "cannot create db folder: " + err.Error()
 		fmt.Println("OpsLog:", a.startupErr)
@@ -1340,6 +1354,11 @@ func copyFileData(src, dst string) error {
 type dbPointer struct {
 	DBPath string         `json:"db_path"`
 	MySQL  *MySQLSettings `json:"mysql,omitempty"`
+	// DeletePending is the previous database file to remove on the NEXT launch —
+	// set by a rename, which can't delete the still-open old file in-process. The
+	// startup path deletes it (with its -wal/-shm sidecars) once the new DB is the
+	// one in use, then clears this.
+	DeletePending string `json:"delete_pending,omitempty"`
 }
 
 func dbPointerPath(dataDir string) string { return filepath.Join(dataDir, "config.json") }
@@ -1653,9 +1672,10 @@ func (a *App) PickSaveDatabase() (string, error) {
 		return "", fmt.Errorf("no app context")
 	}
 	return wruntime.SaveFileDialog(a.ctx, wruntime.SaveDialogOptions{
-		Title:           "Save the OpsLog database to…",
-		DefaultFilename: "opslog.db",
-		Filters:         []wruntime.FileFilter{{DisplayName: "SQLite database (*.db)", Pattern: "*.db"}},
+		Title:            "Save the OpsLog database to…",
+		DefaultDirectory: filepath.Dir(a.dbPath),
+		DefaultFilename:  "opslog.db",
+		Filters:          []wruntime.FileFilter{{DisplayName: "SQLite database (*.db)", Pattern: "*.db"}},
 	})
 }
 
@@ -1697,6 +1717,44 @@ func (a *App) MoveDatabase(dest string) error {
 	return writeDBPointer(a.dataDir, dest)
 }
 
+// RenameDatabase renames the current database file to dest — keeping ALL config
+// (it is the same database under a new name), unlike "New database" which starts
+// empty. Implemented as a consistent copy (VACUUM INTO) plus a switch, then the
+// ORIGINAL file is scheduled for deletion on the next launch (it is open now and
+// can't be removed in-process on Windows). dest must not already exist.
+func (a *App) RenameDatabase(dest string) error {
+	dest = strings.TrimSpace(dest)
+	if dest == "" {
+		return fmt.Errorf("no destination given")
+	}
+	if a.db == nil {
+		return fmt.Errorf("database not open")
+	}
+	old := a.dbPath
+	if strings.EqualFold(filepath.Clean(dest), filepath.Clean(old)) {
+		return fmt.Errorf("that is already the current database name")
+	}
+	if _, err := os.Stat(dest); err == nil {
+		return fmt.Errorf("a file already exists at %s — pick a new name", dest)
+	}
+	if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
+		return fmt.Errorf("create folder: %w", err)
+	}
+	safe := strings.ReplaceAll(dest, "'", "''")
+	if _, err := a.db.ExecContext(a.ctx, "VACUUM INTO '"+safe+"'"); err != nil {
+		return fmt.Errorf("copy database: %w", err)
+	}
+	boot := readBootstrap(a.dataDir)
+	boot.DBPath = dest
+	// Only schedule the old file for deletion when it's a real, on-disk file (a
+	// custom path or the default opslog.db) — never something we somehow share
+	// with the destination.
+	if strings.TrimSpace(old) != "" && !strings.EqualFold(filepath.Clean(old), filepath.Clean(dest)) {
+		boot.DeletePending = old
+	}
+	return writeBootstrap(a.dataDir, boot)
+}
+
 // CreateDatabase creates a fresh, empty logbook at dest (schema migrated) and
 // points OpsLog at it for the next launch. dest must not already exist.
 func (a *App) CreateDatabase(dest string) error {