Add user memory feature for cross-conversation recall

Give the LangChain agent a save_user_memory tool so users can ask it to
remember preferences and personal facts. Memories are stored per-user in
a new user_memories table and injected into the system prompt on each
conversation turn.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

migrations/models/5_20260409215154_add_user_memories.py

@@ -0,0 +1,112 @@
+from tortoise import BaseDBAsyncClient
+
+RUN_IN_TRANSACTION = True
+
+
+async def upgrade(db: BaseDBAsyncClient) -> str:
+    return """
+        CREATE TABLE IF NOT EXISTS "user_memories" (
+    "id" UUID NOT NULL PRIMARY KEY,
+    "content" TEXT NOT NULL,
+    "created_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "user_id" UUID NOT NULL REFERENCES "users" ("id") ON DELETE CASCADE
+);
+        CREATE TABLE IF NOT EXISTS "email_accounts" (
+    "id" UUID NOT NULL PRIMARY KEY,
+    "email_address" VARCHAR(255) NOT NULL UNIQUE,
+    "display_name" VARCHAR(255),
+    "imap_host" VARCHAR(255) NOT NULL,
+    "imap_port" INT NOT NULL DEFAULT 993,
+    "imap_username" VARCHAR(255) NOT NULL,
+    "imap_password" TEXT NOT NULL,
+    "is_active" BOOL NOT NULL DEFAULT True,
+    "last_error" TEXT,
+    "created_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "user_id" UUID NOT NULL REFERENCES "users" ("id") ON DELETE CASCADE
+);
+COMMENT ON TABLE "email_accounts" IS 'Email account configuration for IMAP connections.';
+        CREATE TABLE IF NOT EXISTS "emails" (
+    "id" UUID NOT NULL PRIMARY KEY,
+    "message_id" VARCHAR(255) NOT NULL UNIQUE,
+    "subject" VARCHAR(500) NOT NULL,
+    "from_address" VARCHAR(255) NOT NULL,
+    "to_address" TEXT NOT NULL,
+    "date" TIMESTAMPTZ NOT NULL,
+    "body_text" TEXT,
+    "body_html" TEXT,
+    "chromadb_doc_id" VARCHAR(255),
+    "created_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "expires_at" TIMESTAMPTZ NOT NULL,
+    "account_id" UUID NOT NULL REFERENCES "email_accounts" ("id") ON DELETE CASCADE
+);
+CREATE INDEX IF NOT EXISTS "idx_emails_message_981ddd" ON "emails" ("message_id");
+COMMENT ON TABLE "emails" IS 'Email message metadata and content.';
+        CREATE TABLE IF NOT EXISTS "email_sync_status" (
+    "id" UUID NOT NULL PRIMARY KEY,
+    "last_sync_date" TIMESTAMPTZ,
+    "last_message_uid" INT NOT NULL DEFAULT 0,
+    "message_count" INT NOT NULL DEFAULT 0,
+    "consecutive_failures" INT NOT NULL DEFAULT 0,
+    "last_failure_date" TIMESTAMPTZ,
+    "updated_at" TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "account_id" UUID NOT NULL REFERENCES "email_accounts" ("id") ON DELETE CASCADE
+);
+COMMENT ON TABLE "email_sync_status" IS 'Tracks sync progress and state per email account.';"""
+
+
+async def downgrade(db: BaseDBAsyncClient) -> str:
+    return """
+        DROP TABLE IF EXISTS "user_memories";
+        DROP TABLE IF EXISTS "email_accounts";
+        DROP TABLE IF EXISTS "emails";
+        DROP TABLE IF EXISTS "email_sync_status";"""
+
+
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