feat: implement database schema for merge freeze windows (#819)

[desireddymohithreddy0925]

Closes #819

Description

This PR implements the database schema required for the Configurable Merge Freeze Windows feature.

Changes Made

• Added merge_freeze_windows table to src/lib/db/schema.ts
• Linked freeze windows to githubInstallations for repository-level configuration
• Added fields for cronSchedule, isEmergencyFreeze, and custom freezeMessage

Next Steps

This serves as the foundational data layer. Subsequent PRs will implement the UI settings panel and the backend middleware to block the merge API requests.

Screenshots / UI Thoughts

No UI changes in this PR as this is the backend schema foundation.

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[jakharmonika364]

New file supabase/migrations/0044_merge_freeze_windows.sql (next number after 0043_activity_log_read_at.sql) - creates the table and locks it down like installation_settings:

create table merge_freeze_windows (
  id uuid primary key default gen_random_uuid(),
  installation_id bigint not null references github_installations(id) on delete cascade,
  cron_schedule text,
  is_emergency_freeze boolean not null default false,
  freeze_message text,
  created_at timestamptz not null default now(),
  updated_at timestamptz not null default now()
);

create index merge_freeze_windows_installation_idx on merge_freeze_windows(installation_id);

alter table merge_freeze_windows enable row level security;

create policy merge_freeze_windows_admin_rw on merge_freeze_windows
  for all
  using (
    exists (
      select 1 from github_installation_users giu
      where giu.installation_id = merge_freeze_windows.installation_id
        and giu.user_id = auth.uid()
        and giu.permission_level in ('org_admin', 'repo_admin')
    )
  )
  with check (
    exists (
      select 1 from github_installation_users giu
      where giu.installation_id = merge_freeze_windows.installation_id
        and giu.user_id = auth.uid()
        and giu.permission_level in ('org_admin', 'repo_admin')
    )
  );

[jakharmonika364]

Change the table to the 3-arg form and add an installation index (matches orgCommunities/flaggedAccounts pattern):

Suggested change

	export const mergeFreezeWindows = pgTable('merge_freeze_windows', {
	id: uuid('id').primaryKey().defaultRandom(),
	installationId: bigint('installation_id', { mode: 'number' })
	.notNull()
	.references(() => githubInstallations.id, { onDelete: 'cascade' }),
	cronSchedule: text('cron_schedule'),
	isEmergencyFreeze: boolean('is_emergency_freeze').notNull().default(false),
	freezeMessage: text('freeze_message'),
	createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
	updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
	});
	export const mergeFreezeWindows = pgTable(
	'merge_freeze_windows',
	{
	id: uuid('id').primaryKey().defaultRandom(),
	installationId: bigint('installation_id', { mode: 'number' })
	.notNull()
	.references(() => githubInstallations.id, { onDelete: 'cascade' }),
	cronSchedule: text('cron_schedule'),
	isEmergencyFreeze: boolean('is_emergency_freeze').notNull().default(false),
	freezeMessage: text('freeze_message'),
	createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
	updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
	},
	(t) => ({
	installationIdx: index('merge_freeze_windows_installation_idx').on(t.installationId),
	}),
	);