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>

database/migrations/2026_08_10_091735_create_programs_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('programs', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('user_id')->constrained()->cascadeOnDelete();
+            $table->string('title');
+            $table->text('description')->nullable();
+            $table->unsignedTinyInteger('weeks')->default(4);
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('programs');
+    }
+};

database/migrations/2026_08_10_091736_add_program_scheduling_to_workouts_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('workouts', function (Blueprint $table) {
+            $table->foreignId('program_id')->nullable()->after('user_id')->constrained()->nullOnDelete();
+            $table->unsignedTinyInteger('week_number')->nullable()->after('program_id');
+            $table->unsignedTinyInteger('day_number')->nullable()->after('week_number');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('workouts', function (Blueprint $table) {
+            $table->dropConstrainedForeignId('program_id');
+            $table->dropColumn(['week_number', 'day_number']);
+        });
+    }
+};