Add attachments to service, maintenance, fuel and parts records

Documents already carried a single optional file: upload, download, detach,
access-checked on every request and proxied through this server, so PocketBase's
files are never public URLs. Service records, workshop visits, refills and
catalog parts all want the same thing — a receipt, an invoice, a photo of the
box — so extend it to them.

Rather than copy the document handlers four more times, lift them into one
shared layer. Every attachable collection has a car relation and a file field,
which is what lets a single set of handlers authorize and serve all of them. An
upload finishes by delegating to the collection's own GET handler, so the
response carries the full record — derived fields and all — exactly as a re-read
would. The web side gets the same treatment: one picker component and one
upload-after-save helper behind all five forms. Net effect is five features for
about the cost of the one that was already there.

Alongside:
- parts gain a notes field
- Reminders moves behind Parts catalog in the car detail tabs
- the changed-part labels spell out in full ("Oil & Oil filter" rather than
  "Oil & filter"), and the form and table now agree

The PocketBase schema must be migrated before the new attachments work:
scripts/setup-pocketbase.mjs adds the file fields and parts.notes. It is
additive and safe to re-run.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

API Server/internal/api/records.go

@@ -127,6 +127,7 @@ type serviceRecord struct {
 	ChangedEngineAirFilter bool   `json:"changed_engine_air_filter"`
 	ChangedCabinAirFilter  bool   `json:"changed_cabin_air_filter"`
 	Notes                  string `json:"notes"`
+	File                   string `json:"file"`
 	Created                string `json:"created"`
 	Updated                string `json:"updated"`
 }
@@ -141,11 +142,13 @@ func (rec serviceRecord) toModel() models.ServiceRecord {
 		ChangedEngineAirFilter: rec.ChangedEngineAirFilter,
 		ChangedCabinAirFilter:  rec.ChangedCabinAirFilter,
 		Notes:                  rec.Notes,
+		Attachment:             attachmentOf(rec.File),
 		Created:                rec.Created,
 		Updated:                rec.Updated,
 	}
 }
 
+// servicePayload omits the file field — see attachmentOf.
 func servicePayload(r models.ServiceRecord) map[string]any {
 	return map[string]any{
 		"car":                       r.Car,
@@ -158,6 +161,18 @@ func servicePayload(r models.ServiceRecord) map[string]any {
 	}
 }
 
+// --- attachments ---
+
+// attachmentOf renders a PocketBase file field into the model's attachment pair.
+//
+// It has no counterpart on the write side on purpose: attachments move over
+// multipart via their own endpoint (attachments.go), never as JSON, so a
+// metadata write must not carry a file field that would blank an existing
+// upload.
+func attachmentOf(file string) models.Attachment {
+	return models.Attachment{FileName: file, HasFile: file != ""}
+}
+
 // --- parts ---
 
 type partRecord struct {
@@ -166,6 +181,8 @@ type partRecord struct {
 	Name       string `json:"name"`
 	PartNumber string `json:"part_number"`
 	Category   string `json:"category"`
+	Notes      string `json:"notes"`
+	File       string `json:"file"`
 	Created    string `json:"created"`
 	Updated    string `json:"updated"`
 }
@@ -177,17 +194,21 @@ func (rec partRecord) toModel() models.Part {
 		Name:       rec.Name,
 		PartNumber: rec.PartNumber,
 		Category:   rec.Category,
+		Notes:      rec.Notes,
+		Attachment: attachmentOf(rec.File),
 		Created:    rec.Created,
 		Updated:    rec.Updated,
 	}
 }
 
+// partPayload omits the file field — see attachmentOf.
 func partPayload(p models.Part) map[string]any {
 	return map[string]any{
 		"car":         p.Car,
 		"name":        p.Name,
 		"part_number": p.PartNumber,
 		"category":    p.Category,
+		"notes":       p.Notes,
 	}
 }
 
@@ -224,6 +245,7 @@ type fuelRecord struct {
 	MissedFill bool    `json:"missed_fill"`
 	Station    string  `json:"station"`
 	Notes      string  `json:"notes"`
+	File       string  `json:"file"`
 	Created    string  `json:"created"`
 	Updated    string  `json:"updated"`
 }
@@ -240,11 +262,13 @@ func (rec fuelRecord) toModel() models.FuelEntry {
 		MissedFill: rec.MissedFill,
 		Station:    rec.Station,
 		Notes:      rec.Notes,
+		Attachment: attachmentOf(rec.File),
 		Created:    rec.Created,
 		Updated:    rec.Updated,
 	}
 }
 
+// fuelPayload omits the file field — see attachmentOf.
 func fuelPayload(f models.FuelEntry) map[string]any {
 	return map[string]any{
 		"car":         f.Car,
@@ -277,6 +301,7 @@ type maintenanceRecord struct {
 	InvoiceNumber string  `json:"invoice_number"`
 	WarrantyUntil string  `json:"warranty_until"`
 	Notes         string  `json:"notes"`
+	File          string  `json:"file"`
 	Created       string  `json:"created"`
 	Updated       string  `json:"updated"`
 }
@@ -298,11 +323,13 @@ func (rec maintenanceRecord) toModel() models.MaintenanceEntry {
 		InvoiceNumber: rec.InvoiceNumber,
 		WarrantyUntil: parsePBDatePtr(rec.WarrantyUntil),
 		Notes:         rec.Notes,
+		Attachment:    attachmentOf(rec.File),
 		Created:       rec.Created,
 		Updated:       rec.Updated,
 	}
 }
 
+// maintenancePayload omits the file field — see attachmentOf.
 func maintenancePayload(m models.MaintenanceEntry) map[string]any {
 	return map[string]any{
 		"car":            m.Car,
@@ -352,15 +379,13 @@ func (rec documentRecord) toModel() models.CarDocument {
 		ExpiryDate: parsePBDatePtr(rec.ExpiryDate),
 		Cost:       rec.Cost,
 		Notes:      rec.Notes,
-		FileName:   rec.File,
-		HasFile:    rec.File != "",
+		Attachment: attachmentOf(rec.File),
 		Created:    rec.Created,
 		Updated:    rec.Updated,
 	}
 }
 
-// documentPayload omits the file field: attachments move over multipart, never
-// as JSON, so a metadata write must not blank an existing upload.
+// documentPayload omits the file field — see attachmentOf.
 func documentPayload(d models.CarDocument) map[string]any {
 	return map[string]any{
 		"car":         d.Car,