Add DB migrations and run them on startup

Enable sqlx "migrate" feature and add SQL migrations to create the
database schema: pg_trgm extension, sources, genres, authors, sequences,
books, junction tables, annotations, and supporting indexes

migrations/20260116092207_create_books_table.sql

@@ -0,0 +1,20 @@
+-- Create books table
+CREATE TABLE IF NOT EXISTS books (
+    id SERIAL PRIMARY KEY,
+    source SMALLINT NOT NULL,
+    remote_id INTEGER NOT NULL,
+    title VARCHAR(256) NOT NULL,
+    lang VARCHAR(3) NOT NULL,
+    file_type VARCHAR(4) NOT NULL,
+    uploaded DATE NOT NULL,
+    is_deleted BOOLEAN NOT NULL DEFAULT false,
+    pages INTEGER,
+    year SMALLINT NOT NULL DEFAULT 0,
+    CONSTRAINT uc_books_source_remote_id UNIQUE (source, remote_id),
+    CONSTRAINT fk_books_sources_id_source FOREIGN KEY (source) REFERENCES sources(id)
+);
+
+-- Create indexes for books
+CREATE INDEX IF NOT EXISTS idx_id_asc__not_is_deleted ON books (id) WHERE NOT is_deleted;
+CREATE INDEX IF NOT EXISTS idx_id_asc__uploaded__not_is_deleted ON books (id, uploaded) WHERE NOT is_deleted;
+CREATE INDEX IF NOT EXISTS idx_uploaded__id_asc__not_is_deleted ON books (uploaded, id) WHERE NOT is_deleted;