refactor(llm): use column constants in schema notes

Added missing column constants to data.models.go:
- ColBudgetCents, ColTotalCents (money columns)
- ColLastServicedAt (maintenance scheduling)
- ColProjectTypeID (FK reference)

Used these constants in LLM schema notes so column renames are
caught at compile time. Left few-shot examples as raw strings
since they're illustrative examples, not operational code.

This follows the pattern established in b0f1942 where column
constants centralize SQL column references.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: cpcloud

internal/data/models.go

@@ -38,14 +38,18 @@ const (
 	ColDeletedAt         = "deleted_at"
 	ColStatus            = "status"
 	ColActualCents       = "actual_cents"
+	ColBudgetCents       = "budget_cents"
 	ColCostCents         = "cost_cents"
+	ColTotalCents        = "total_cents"
 	ColIntervalMonths    = "interval_months"
+	ColLastServicedAt    = "last_serviced_at"
 	ColWarrantyExpiry    = "warranty_expiry"
 	ColServicedAt        = "serviced_at"
 	ColReceivedDate      = "received_date"
 	ColRestoredAt        = "restored_at"
 	ColVendorID          = "vendor_id"
 	ColProjectID         = "project_id"
+	ColProjectTypeID     = "project_type_id"
 	ColApplianceID       = "appliance_id"
 	ColMaintenanceItemID = "maintenance_item_id"
 	ColEntity            = "entity"

internal/llm/prompt.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"strings"
 	"time"
+
+	"github.com/cpcloud/micasa/internal/data"
 )
 
 // TableInfo describes a database table for context injection.
@@ -255,9 +257,9 @@ RULES:
 
 const sqlSchemaNotes = `
 Notes:
-- Maintenance scheduling: next_due = date(last_serviced_at, '+' || interval_months || ' months')
+- Maintenance scheduling: next_due = date(` + data.ColLastServicedAt + `, '+' || ` + data.ColIntervalMonths + ` || ' months')
 - Project statuses: ideating, planned, quoted, underway, delayed, completed, abandoned
-- Warranty expiry is in the warranty_expiry column (date string)
+- Warranty expiry is in the ` + data.ColWarrantyExpiry + ` column (date string)
 - For case-insensitive text search, use UPPER() or LOWER() on both sides: WHERE LOWER(title) LIKE LOWER('%hvac%')`
 
 const sqlFewShot = `## Examples