feat(api): GET /api/me

Returns the authenticated user (id/username/is_admin). Shape
matches UserView used in the login response so SPA stores stay
typed against one interface.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/api/api.go

@@ -6,7 +6,6 @@ package api
 
 import (
 	"log/slog"
-	"net/http"
 
 	"github.com/go-chi/chi/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -33,10 +32,3 @@ type handlers struct {
 	pool   *pgxpool.Pool
 	logger *slog.Logger
 }
-
-// Stub handlers so Mount() compiles. Real implementations in later tasks
-// replace these in place (Task 8 me).
-
-func (h *handlers) handleGetMe(w http.ResponseWriter, r *http.Request) {
-	writeErr(w, http.StatusNotImplemented, "not_implemented", "me not wired")
-}