remove all foreign key constraints from SQL migrations

Foreign keys at the database level cause issues with deployment flexibility.
Keep only indexes for query performance; enforce referential integrity at
the application level.

libs/migrate/sql/m20250628_000080_add_message_reactions_and_search.sql

@@ -2,9 +2,9 @@
 CREATE TABLE IF NOT EXISTS room_message_reaction
 (
     id         UUID PRIMARY KEY,
-    room       UUID                     NOT NULL REFERENCES room (id) ON DELETE CASCADE,
+    room       UUID                     NOT NULL,
-    message    UUID                     NOT NULL REFERENCES room_message (id) ON DELETE CASCADE,
+    message    UUID                     NOT NULL,
-    "user"     UUID                     NOT NULL REFERENCES "user" (uid) ON DELETE CASCADE,
+    "user"     UUID                     NOT NULL,
     emoji      VARCHAR(50)              NOT NULL,
     created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
     UNIQUE (message, "user", emoji)

libs/migrate/sql/m20250628_000081_add_message_edit_history.sql

@@ -1,8 +1,8 @@
 CREATE TABLE IF NOT EXISTS room_message_edit_history
 (
     id          UUID PRIMARY KEY,
-    message     UUID                     NOT NULL REFERENCES room_message (id) ON DELETE CASCADE,
+    message     UUID                     NOT NULL,
-    "user"      UUID                     NOT NULL REFERENCES "user" (uid) ON DELETE CASCADE,
+    "user"      UUID                     NOT NULL,
     old_content TEXT                     NOT NULL,
     new_content TEXT                     NOT NULL,
     edited_at   TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()

libs/migrate/sql/m20260407_000002_create_project_board.sql

@@ -14,7 +14,7 @@ CREATE INDEX IF NOT EXISTS idx_project_board_project ON project_board (project_u
 CREATE TABLE IF NOT EXISTS project_board_column
 (
     id         UUID PRIMARY KEY      DEFAULT gen_random_uuid(),
-    board_uuid UUID         NOT NULL REFERENCES project_board (id) ON DELETE CASCADE,
+    board_uuid UUID         NOT NULL,
     name       VARCHAR(255) NOT NULL,
     position   INTEGER      NOT NULL DEFAULT 0,
     wip_limit  INTEGER,
@@ -26,7 +26,7 @@ CREATE INDEX IF NOT EXISTS idx_project_board_column_board ON project_board_colum
 CREATE TABLE IF NOT EXISTS project_board_card
 (
     id          UUID PRIMARY KEY      DEFAULT gen_random_uuid(),
-    column_uuid UUID         NOT NULL REFERENCES project_board_column (id) ON DELETE CASCADE,
+    column_uuid UUID         NOT NULL,
     issue_id    BIGINT,
     project     UUID,
     title       VARCHAR(500) NOT NULL,

libs/migrate/sql/m20260411_000003_add_workspace_id_to_project.sql

@@ -1,4 +1,4 @@
 ALTER TABLE project
-    ADD COLUMN workspace_id UUID REFERENCES workspace(id) ON DELETE SET NULL;
+    ADD COLUMN workspace_id UUID;
 
 CREATE INDEX idx_project_workspace_id ON project (workspace_id) WHERE workspace_id IS NOT NULL;

libs/migrate/sql/m20260412_000001_create_workspace_billing.sql

@@ -1,5 +1,5 @@
 CREATE TABLE IF NOT EXISTS workspace_billing (
-    workspace_id       UUID PRIMARY KEY REFERENCES workspace(id) ON DELETE CASCADE,
+    workspace_id       UUID PRIMARY KEY,
     balance            DECIMAL(20, 4) NOT NULL DEFAULT 0,
     currency           VARCHAR(10)    NOT NULL DEFAULT 'USD',
     monthly_quota      DECIMAL(20, 4) NOT NULL DEFAULT 0,

libs/migrate/sql/m20260412_000002_create_workspace_billing_history.sql

@@ -1,7 +1,7 @@
 CREATE TABLE IF NOT EXISTS workspace_billing_history
 (
     uid          UUID PRIMARY KEY,
-    workspace_id UUID           NOT NULL REFERENCES workspace (id) ON DELETE CASCADE,
+    workspace_id UUID           NOT NULL,
     user_id      UUID,
     amount       DECIMAL(20, 4) NOT NULL,
     currency     VARCHAR(10)    NOT NULL DEFAULT 'USD',

libs/migrate/sql/m20260414_000001_create_agent_task.sql

@@ -22,9 +22,7 @@ CREATE TABLE IF NOT EXISTS agent_task
     started_at     TIMESTAMPTZ,
     done_at        TIMESTAMPTZ,
     -- Progress info (step count, current status text)
-    progress       VARCHAR(255),
+    progress       VARCHAR(255)
-    -- Parent task FK
-    CONSTRAINT fk_agent_task_parent FOREIGN KEY (parent_id) REFERENCES agent_task(id) ON DELETE SET NULL
 );
 
 CREATE INDEX IF NOT EXISTS idx_agent_task_project ON agent_task (project_uuid);