Add multi-week workout programs

A Workout was a single flat session with no way to schedule several
across weeks/days as a structured plan (e.g. Push/Pull/Legs over 4
weeks) - every user started from a blank builder each time, and there
was no template concept at all.

Adds a Program (title, description, week count) that Workouts can
optionally belong to via nullable program_id/week_number/day_number
columns, reusing all existing workout and session-tracking
infrastructure rather than building a parallel system. The program show
page lays out the schedule week by week and derives progress (completed
vs total) from the user's existing WorkoutSession completions - no new
enrollment/progress-tracking concept needed. Deleting a program
unschedules its workouts (nullOnDelete) rather than destroying them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lang/ro/app.php

@@ -8,6 +8,7 @@ return [
         'blog' => 'Blog',
             'build_workout' => 'Creează un antrenament',
             'dashboard' => 'Tabloul de bord',
+            'programs' => 'Programe',
             'admin' => 'Admin',
         'profile' => 'Profil',
         'logout' => 'Deconectare',