Initial commit

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

backend/db/migrations/001_create_exercises.up.sql

@@ -0,0 +1,16 @@
+CREATE TABLE exercises (
+    id           INTEGER PRIMARY KEY AUTOINCREMENT,
+    name         TEXT NOT NULL CHECK(length(name) >= 1 AND length(name) <= 100),
+    description  TEXT DEFAULT '',
+    muscle_group TEXT NOT NULL CHECK(muscle_group IN (
+        'brust', 'ruecken', 'schultern', 'bizeps', 'trizeps',
+        'beine', 'bauch', 'ganzkoerper', 'sonstiges'
+    )),
+    weight_step_kg REAL NOT NULL DEFAULT 2.5 CHECK(weight_step_kg > 0),
+    created_at   DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at   DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    deleted_at   DATETIME
+);
+
+CREATE INDEX idx_exercises_muscle_group ON exercises(muscle_group) WHERE deleted_at IS NULL;
+CREATE INDEX idx_exercises_deleted_at ON exercises(deleted_at);