Add timetable scheduler Phases 1 + 2 to school-service

Phase 1 — Stammdaten (7 tables):
  tt_class, tt_period, tt_room, tt_subject, tt_teacher,
  tt_curriculum, tt_assignment with CRUD endpoints.

Phase 2 — Constraints (15 typed tables):
  Teacher (6): unavailable_day, unavailable_window, max_hours_day,
    max_hours_week, excluded_subject, excluded_room
  Subject (5): min_day_gap, max_consecutive, contiguous_when_repeated,
    preferred_period, double_lesson
  Class (2): max_hours_day, no_gaps
  Room (2): requires_type, unavailable

Each constraint row carries is_hard / weight / active / note /
created_by_user_id; ownership enforced via WHERE EXISTS against the
parent tt_teacher/tt_class/tt_subject/tt_room row.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

school-service/internal/database/timetable_migrations.go

@@ -0,0 +1,104 @@
+package database
+
+// TimetableMigrations returns the SQL statements that create all timetable-related
+// tables. They are applied idempotently via CREATE TABLE IF NOT EXISTS.
+func TimetableMigrations() []string {
+	return []string{
+		// Classes (school-wide, distinct from per-teacher `classes` table)
+		`CREATE TABLE IF NOT EXISTS tt_class (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			created_by_user_id UUID NOT NULL,
+			name VARCHAR(50) NOT NULL,
+			grade_level INT NOT NULL,
+			student_count INT DEFAULT 0,
+			notes TEXT,
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(created_by_user_id, name)
+		)`,
+
+		// Time periods (Mon=1..Sun=7, period_index = 1..N)
+		`CREATE TABLE IF NOT EXISTS tt_period (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			created_by_user_id UUID NOT NULL,
+			day_of_week INT NOT NULL CHECK (day_of_week BETWEEN 1 AND 7),
+			period_index INT NOT NULL CHECK (period_index >= 1),
+			start_time TIME NOT NULL,
+			end_time TIME NOT NULL,
+			is_break BOOLEAN DEFAULT false,
+			label VARCHAR(50),
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(created_by_user_id, day_of_week, period_index)
+		)`,
+
+		// Rooms
+		`CREATE TABLE IF NOT EXISTS tt_room (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			created_by_user_id UUID NOT NULL,
+			name VARCHAR(50) NOT NULL,
+			room_type VARCHAR(30),
+			capacity INT DEFAULT 30,
+			floor_level INT DEFAULT 0,
+			has_elevator BOOLEAN DEFAULT true,
+			notes TEXT,
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(created_by_user_id, name)
+		)`,
+
+		// Subjects (school-wide, distinct from per-teacher `subjects`)
+		`CREATE TABLE IF NOT EXISTS tt_subject (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			created_by_user_id UUID NOT NULL,
+			name VARCHAR(100) NOT NULL,
+			short_code VARCHAR(10) NOT NULL,
+			color VARCHAR(7),
+			is_main_subject BOOLEAN DEFAULT false,
+			required_room_type VARCHAR(30),
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(created_by_user_id, short_code)
+		)`,
+
+		// Teachers (planning resource, NOT a BreakPilot user)
+		`CREATE TABLE IF NOT EXISTS tt_teacher (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			created_by_user_id UUID NOT NULL,
+			first_name VARCHAR(100) NOT NULL,
+			last_name VARCHAR(100) NOT NULL,
+			short_code VARCHAR(10) NOT NULL,
+			employment_percentage INT DEFAULT 100,
+			max_hours_week INT DEFAULT 28,
+			notes TEXT,
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(created_by_user_id, short_code)
+		)`,
+
+		// Curriculum: weekly hour count per class+subject
+		`CREATE TABLE IF NOT EXISTS tt_curriculum (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			class_id UUID NOT NULL REFERENCES tt_class(id) ON DELETE CASCADE,
+			subject_id UUID NOT NULL REFERENCES tt_subject(id) ON DELETE CASCADE,
+			weekly_hours INT NOT NULL CHECK (weekly_hours >= 1),
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(class_id, subject_id)
+		)`,
+
+		// Assignment: which teacher teaches which subject in which class
+		`CREATE TABLE IF NOT EXISTS tt_assignment (
+			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+			teacher_id UUID NOT NULL REFERENCES tt_teacher(id) ON DELETE CASCADE,
+			class_id UUID NOT NULL REFERENCES tt_class(id) ON DELETE CASCADE,
+			subject_id UUID NOT NULL REFERENCES tt_subject(id) ON DELETE CASCADE,
+			created_at TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(teacher_id, class_id, subject_id)
+		)`,
+
+		// Indexes
+		`CREATE INDEX IF NOT EXISTS idx_tt_class_user ON tt_class(created_by_user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_period_user ON tt_period(created_by_user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_room_user ON tt_room(created_by_user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_subject_user ON tt_subject(created_by_user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_teacher_user ON tt_teacher(created_by_user_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_curriculum_class ON tt_curriculum(class_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_assignment_teacher ON tt_assignment(teacher_id)`,
+		`CREATE INDEX IF NOT EXISTS idx_tt_assignment_class ON tt_assignment(class_id)`,
+	}
+}