Add budget/availability model types

Add EstimatedMinutes to Task, BudgetTracked to Project and LabelColor
structs. Create budget.go with AvailabilityBlock, BudgetPeriod, and
BudgetStatus types for modeling task budgets and calendar availability.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PQaPGQVSfmKUiHXB87qRTC

1 files changed, 28 insertions, 0 deletions

diff --git a/internal/models/budget.go b/internal/models/budget.go
new file mode 100644
index 0000000..8a3917a
--- /dev/null
+++ b/internal/models/budget.go
@@ -0,0 +1,28 @@
+package models
+
+// AvailabilityBlock is one recurring weekly window of time the user has
+// manually declared as available (e.g. "weekday evenings 18:00-20:00").
+// Reduced by real calendar events at computation time -- see
+// handlers.ComputeBudgetPeriod.
+type AvailabilityBlock struct {
+	ID        string `json:"id"`
+	Weekday   int    `json:"weekday"` // 0-6, Sun-Sat
+	StartTime string `json:"start_time"` // "18:00"
+	EndTime   string `json:"end_time"`   // "20:00"
+	Label     string `json:"label"`
+}
+
+// BudgetPeriod is the scheduled-vs-available load for one window of time.
+// Purely informational -- no field here ever drives auto-scheduling.
+type BudgetPeriod struct {
+	ScheduledMinutes int `json:"scheduled_minutes"`
+	AvailableMinutes int `json:"available_minutes"`
+}
+
+// BudgetStatus bundles today's and this rolling week's load. Only present
+// on API responses when at least one budget-tracked task exists in the
+// wider (Week) window.
+type BudgetStatus struct {
+	Today BudgetPeriod `json:"today"`
+	Week  BudgetPeriod `json:"week"`
+}