feat(modules): module topics for student form, admin CRUD with pagination

- db: modules table (name, lessons_count) + entries.module_id (ON DELETE SET NULL), migration + idempotent startup ensure
- api: GET /api/modules (public, search + limit/offset, entries_count), POST/PUT/DELETE (admin, audit-logged)
- entries: accept/validate module_id on create/update, return module_name, module_id filter
- backup/restore: include modules and entries.module_id
- student form: required module select, hidden while no modules exist
- admin: modules.html + js/modules.js list with pagination, search, create/edit/delete modal
- journal: module filter, module select in edit modal, module badge, CSV column

db/init.sql

@@ -24,6 +24,13 @@ CREATE TABLE IF NOT EXISTS groups (
   cover_path VARCHAR(255)
 );
 
+CREATE TABLE IF NOT EXISTS modules (
+  id SERIAL PRIMARY KEY,
+  name VARCHAR(200) NOT NULL UNIQUE,
+  lessons_count INT NOT NULL DEFAULT 0,
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
 CREATE TABLE IF NOT EXISTS students (
   id SERIAL PRIMARY KEY,
   name VARCHAR(150) NOT NULL UNIQUE,
@@ -35,6 +42,7 @@ CREATE TABLE IF NOT EXISTS entries (
   id SERIAL PRIMARY KEY,
   student_name VARCHAR(150) NOT NULL,
   group_id INT NOT NULL REFERENCES groups(id),
+  module_id INT REFERENCES modules(id) ON DELETE SET NULL,
   description TEXT NOT NULL,
   description_original TEXT,
   description_ai TEXT,
@@ -52,8 +60,10 @@ ALTER TABLE entries ADD COLUMN IF NOT EXISTS description_ai TEXT;
 ALTER TABLE entries ADD COLUMN IF NOT EXISTS ai_status VARCHAR(20) NOT NULL DEFAULT 'pending';
 ALTER TABLE entries ADD COLUMN IF NOT EXISTS ai_checked_at TIMESTAMPTZ;
 ALTER TABLE entries ADD COLUMN IF NOT EXISTS ai_error TEXT;
+ALTER TABLE entries ADD COLUMN IF NOT EXISTS module_id INT REFERENCES modules(id) ON DELETE SET NULL;
 
 CREATE INDEX IF NOT EXISTS idx_entries_ai_pending ON entries(id) WHERE ai_status = 'pending' AND deleted_at IS NULL;
+CREATE INDEX IF NOT EXISTS idx_entries_module_id ON entries(module_id);
 
 CREATE OR REPLACE FUNCTION notify_entries_changed() RETURNS trigger AS $$
 BEGIN

db/migration.sql

@@ -223,3 +223,13 @@ ON CONFLICT (key) DO NOTHING;
 
 ALTER TABLE entries ADD COLUMN IF NOT EXISTS photo_original_path VARCHAR(255);
 ALTER TABLE photo_jobs ADD COLUMN IF NOT EXISTS applied BOOLEAN NOT NULL DEFAULT false;
+
+CREATE TABLE IF NOT EXISTS modules (
+  id SERIAL PRIMARY KEY,
+  name VARCHAR(200) NOT NULL UNIQUE,
+  lessons_count INT NOT NULL DEFAULT 0,
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
+ALTER TABLE entries ADD COLUMN IF NOT EXISTS module_id INT REFERENCES modules(id) ON DELETE SET NULL;
+CREATE INDEX IF NOT EXISTS idx_entries_module_id ON entries(module_id);