refactor: modularize email module and use actor for email verification (#1625)

backend/resources/migrations/sqlite/20260727120000_email_verification_actors.down.sql

@@ -0,0 +1,17 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+CREATE TABLE email_verification_tokens
+(
+    id         TEXT PRIMARY KEY,
+    created_at DATETIME NOT NULL,
+    token      TEXT     NOT NULL UNIQUE,
+    expires_at DATETIME NOT NULL,
+    user_id    TEXT     NOT NULL,
+    FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE
+);
+
+CREATE INDEX idx_email_verification_tokens_expires_at ON email_verification_tokens (expires_at);
+
+COMMIT;
+PRAGMA foreign_keys=ON;

backend/resources/migrations/sqlite/20260727120000_email_verification_actors.up.sql

@@ -0,0 +1,7 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+DROP TABLE email_verification_tokens;
+
+COMMIT;
+PRAGMA foreign_keys=ON;