Implement budget tracking data structures and database functions

[Claude]

Adds the foundation for budget tracking functionality to enable users to set monthly budgets per account and compare against actual spending.

Changes

Data Models (src/cloud/mod.rs)

• BudgetInfo: Stores budget configuration (monthly_budget, currency, alert_threshold)
• BudgetStatus: Computed comparison of budget vs actual with alert state

Database Schema (src/db.rs)

• budgets table with account-level budget storage and foreign key constraints
• Supports configurable alert thresholds (default 80%)

CRUD Operations (src/db.rs)

• save_budget() / get_budget() / get_all_budgets() / delete_budget()
• get_budget_status(): Calculates percentage used, remaining budget, alert status
• get_all_budget_statuses(): Batch status computation
• Integrates with existing cost cache infrastructure for performance

Example Usage

use chrono::Utc;
use crate::cloud::BudgetInfo;
use crate::db::{save_budget, get_budget_status};

// Set a budget
let budget = BudgetInfo {
    account_id: "account-123".to_string(),
    monthly_budget: 1000.0,
    currency: "USD".to_string(),
    alert_threshold: 80.0,
    created_at: Utc::now(),
    updated_at: Utc::now(),
};
save_budget(&budget)?;

// Check status
let status = get_budget_status("account-123")?;
// status.percentage_used, status.remaining, status.alert_triggered

UI integration and budget management features are not included in this PR.

[Copilot]

Pull request overview

Adds the foundational data model + persistence layer for per-account monthly budgets, enabling later UI/features to compare current-month spend vs configured budget and trigger alerts.

Changes:

• Introduces BudgetInfo and BudgetStatus models for budget configuration and computed status.
• Adds a budgets table to DuckDB and implements budget CRUD helpers.
• Adds budget status computation using cached cost summaries.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/db.rs	Creates budgets table and adds budget CRUD + status computation functions.
src/cloud/mod.rs	Adds budget-related structs (BudgetInfo, BudgetStatus) to shared cloud models.

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[Copilot]

The new budgets table adds a foreign key to cloud_accounts(id), but delete_account() currently deletes from cost_data only before removing the account. If foreign keys are enforced, deleting an account with an existing budget row will fail. Consider deleting from budgets in delete_account() as well (or adding ON DELETE CASCADE for the FK if that matches the intended behavior).

Suggested change

	FOREIGN KEY (account_id) REFERENCES cloud_accounts(id)
	FOREIGN KEY (account_id) REFERENCES cloud_accounts(id) ON DELETE CASCADE

[Copilot]

get_budget_status() loads all accounts via get_all_accounts() and then searches for the matching ID. This is inefficient and will become noticeably slower as the number of accounts grows; it also does extra secret-store work done by get_all_accounts(). Prefer a targeted query to fetch just the account name/provider for account_id (or a dedicated get_account_by_id helper) instead of loading the full list.

[Copilot]

The error returned when an account is missing is too generic for troubleshooting. Including the account_id in the message (and ideally clarifying whether it was missing from cloud_accounts) would make logs and UI errors much easier to diagnose.

Suggested change

	.ok_or_else(|| anyhow::anyhow!("Account not found"))?;
	.ok_or_else(|| {
	anyhow::anyhow!(
	"Account with id '{}' not found in cloud_accounts while computing budget status",
	account_id
	)
	})?;

[Copilot]

get_all_budget_statuses() calls get_budget_status() per budget, and get_budget_status() re-queries the budget and re-loads all accounts each time. This creates an N+1 pattern and can result in a lot of redundant DB/keyring work. Consider computing statuses in batch: fetch all accounts once (or build a map), reuse the BudgetInfo already loaded, and then look up cached summaries per account.