Initial commit MKD fixes

backend/migrations/create_application_comments_history.sql

@@ -0,0 +1,25 @@
+-- Комментарии к заявкам (внутренние и с жителем)
+CREATE TABLE IF NOT EXISTS application_comments (
+  id             BIGSERIAL PRIMARY KEY,
+  application_id BIGINT NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+  author_name    TEXT NOT NULL,
+  type           VARCHAR(20) NOT NULL DEFAULT 'internal',
+  text           TEXT NOT NULL,
+  created_at     TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_application_comments_app ON application_comments(application_id);
+CREATE INDEX IF NOT EXISTS idx_application_comments_type ON application_comments(type);
+
+-- История изменений заявки
+CREATE TABLE IF NOT EXISTS application_history (
+  id             BIGSERIAL PRIMARY KEY,
+  application_id BIGINT NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+  changed_by     TEXT NOT NULL,
+  changed_at     TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  field_name     TEXT NOT NULL,
+  old_value      TEXT,
+  new_value      TEXT
+);
+
+CREATE INDEX IF NOT EXISTS idx_application_history_app ON application_history(application_id);