feat: add psql shell and username-to-shell routing

Add a PostgreSQL psql interactive terminal shell with backslash
meta-commands, SQL statement handling with multi-line buffering, and
canned responses for common queries. Add username-based shell routing
via [shell.username_routes] config (second priority after credential-
specific shell, before random selection). Bump version to 0.13.0.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/server/server.go

@@ -24,6 +24,7 @@ import (
 	"git.t-juice.club/torjus/oubliette/internal/shell/bash"
 	"git.t-juice.club/torjus/oubliette/internal/shell/cisco"
 	"git.t-juice.club/torjus/oubliette/internal/shell/fridge"
+	psqlshell "git.t-juice.club/torjus/oubliette/internal/shell/psql"
 	"git.t-juice.club/torjus/oubliette/internal/storage"
 	"golang.org/x/crypto/ssh"
 )
@@ -58,6 +59,9 @@ func New(cfg config.Config, store storage.Store, logger *slog.Logger, m *metrics
 	if err := registry.Register(cisco.NewCiscoShell(), 1); err != nil {
 		return nil, fmt.Errorf("registering cisco shell: %w", err)
 	}
+	if err := registry.Register(psqlshell.NewPsqlShell(), 1); err != nil {
+		return nil, fmt.Errorf("registering psql shell: %w", err)
+	}
 
 	geo, err := geoip.New()
 	if err != nil {
@@ -185,6 +189,18 @@ func (s *Server) handleSession(channel ssh.Channel, requests <-chan *ssh.Request
 			s.logger.Warn("configured shell not found, falling back to random", "shell", shellName)
 		}
 	}
+	// Second priority: username-based route.
+	if selectedShell == nil {
+		if shellName, ok := s.cfg.Shell.UsernameRoutes[conn.User()]; ok {
+			sh, found := s.shellRegistry.Get(shellName)
+			if found {
+				selectedShell = sh
+			} else {
+				s.logger.Warn("username route shell not found, falling back to random", "shell", shellName, "user", conn.User())
+			}
+		}
+	}
+	// Lowest priority: random selection.
 	if selectedShell == nil {
 		var err error
 		selectedShell, err = s.shellRegistry.Select()