feat(core): consolidate auth service into backend and implement stripe billing

This commit performs a major architectural refactor by migrating the standalone `auth-service` into the main `backend` application, enabling a unified codebase and simplified deployment. It also introduces comprehensive Stripe billing support and a new administrative dashboard.

Key changes:
- **Architecture**: Deleted `apps/auth-service` and integrated its functionality (JWT, magic links, OAuth, user management) into `apps/backend`.
- **Billing**: Added Stripe integration to `backend`, supporting both monthly and yearly subscription cycles with automatic plan entitlement enforcement (e.g., location limits).
- **Admin Dashboard**: Implemented a new administrative service and API endpoints to manage tenants, users, and view platform-wide statistics.
- **Frontend**:
    - Added a new pricing page with monthly/yearly toggle and comparison table.
    - Integrated Stripe and Sentry for payments and error tracking.
    - Improved dashboard UX/UI and added i18n support for new features.
    - Enhanced the public booking flow with better validation and contact form integration.
- **Database**: Added migrations for users, magic links, password resets, OAuth states, admin audit logs, and refresh tokens.
- **DevOps**: Updated environment configurations for Railway and Vercel, and streamlined the project's `package.json` scripts.

apps/backend/migrations/00006_auth_and_admin.sql

@@ -0,0 +1,97 @@
+-- +goose Up
+-- +goose StatementBegin
+
+-- Users table for authentication (migrated from auth-service)
+CREATE TABLE IF NOT EXISTS users (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    email VARCHAR(255) NOT NULL UNIQUE,
+    name VARCHAR(255),
+    password_hash VARCHAR(255),
+    email_verified BOOLEAN DEFAULT FALSE,
+    provider VARCHAR(50) NOT NULL DEFAULT 'email',
+    provider_id VARCHAR(255),
+    role VARCHAR(50) NOT NULL DEFAULT 'user',
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    last_login_at TIMESTAMP WITH TIME ZONE
+);
+
+CREATE INDEX IF NOT EXISTS idx_users_email ON users(email);
+CREATE INDEX IF NOT EXISTS idx_users_provider ON users(provider, provider_id);
+CREATE INDEX IF NOT EXISTS idx_users_role ON users(role);
+
+-- Magic links for passwordless auth
+CREATE TABLE IF NOT EXISTS magic_links (
+    token VARCHAR(255) PRIMARY KEY,
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    email VARCHAR(255) NOT NULL,
+    used BOOLEAN DEFAULT FALSE,
+    expires_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_magic_links_user_id ON magic_links(user_id);
+CREATE INDEX IF NOT EXISTS idx_magic_links_expires ON magic_links(expires_at) WHERE used = FALSE;
+
+-- Password reset tokens
+CREATE TABLE IF NOT EXISTS password_resets (
+    token VARCHAR(255) PRIMARY KEY,
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    expires_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    used BOOLEAN DEFAULT FALSE,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_password_resets_user_id ON password_resets(user_id);
+
+-- OAuth state tokens
+CREATE TABLE IF NOT EXISTS oauth_states (
+    state VARCHAR(255) PRIMARY KEY,
+    redirect_url VARCHAR(500),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    expires_at TIMESTAMP WITH TIME ZONE NOT NULL
+);
+
+-- Admin audit log
+CREATE TABLE IF NOT EXISTS admin_audit_log (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    admin_user_id UUID REFERENCES users(id) ON DELETE SET NULL,
+    action VARCHAR(100) NOT NULL,
+    resource_type VARCHAR(100),
+    resource_id VARCHAR(255),
+    details JSONB,
+    ip_address VARCHAR(45),
+    user_agent TEXT,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_admin_audit_log_admin ON admin_audit_log(admin_user_id);
+CREATE INDEX IF NOT EXISTS idx_admin_audit_log_action ON admin_audit_log(action);
+CREATE INDEX IF NOT EXISTS idx_admin_audit_log_created ON admin_audit_log(created_at);
+
+-- Refresh tokens for JWT
+CREATE TABLE IF NOT EXISTS refresh_tokens (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    token_hash VARCHAR(255) NOT NULL UNIQUE,
+    expires_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    revoked BOOLEAN DEFAULT FALSE,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_refresh_tokens_user ON refresh_tokens(user_id);
+CREATE INDEX IF NOT EXISTS idx_refresh_tokens_hash ON refresh_tokens(token_hash);
+
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+
+DROP TABLE IF EXISTS refresh_tokens;
+DROP TABLE IF EXISTS admin_audit_log;
+DROP TABLE IF EXISTS oauth_states;
+DROP TABLE IF EXISTS password_resets;
+DROP TABLE IF EXISTS magic_links;
+DROP TABLE IF EXISTS users;
+
+-- +goose StatementEnd