Add technical check history

A car's mandatory roadworthiness inspections — przegląd techniczny, MOT,
TÜV — had nowhere to live. Log them behind Service history, which this
mirrors minus the odometer: an inspection falls due on a date whatever
the mileage reads.

The cycle is legal rather than mechanical, and it is not constant — a new
car's first check falls due years later than its third. So the car's
technical_check_interval_days only prefills the next date, and any check
overrides it with the valid-until printed on its own certificate. A
failed check derives no next date at all: reading one off a failure would
stamp a reassuring "valid until" on a car that just flunked.

The next-due date and its status are derived on every read rather than
stored, for the same reason documents are — a stored verdict goes stale
as the date passes. The response carries the same expiry shape documents
use, so the web app reuses the existing badge rather than growing a
second one.

Each check records result, cost, station and notes, and holds the
certificate as its single attachment on the same terms as every other
record.

Needs `node scripts/setup-pocketbase.mjs` to create technical_checks and
add the interval to cars. The reformatting in records.go is gofmt
realigning the car struct around a longer field name.

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

Web App/web/src/components/CarFormModal.vue

@@ -27,6 +27,7 @@ const form = ref({
   coolantSpec: props.car?.coolantSpec ?? "",
   serviceIntervalDays: props.car?.serviceIntervalDays || 365,
   serviceIntervalKm: props.car?.serviceIntervalKm || 15000,
+  technicalCheckIntervalDays: props.car?.technicalCheckIntervalDays || 365,
   currentKm: props.car?.currentKm || "",
 });
 
@@ -52,6 +53,7 @@ async function submit() {
       coolantSpec: form.value.coolantSpec.trim(),
       serviceIntervalDays: Number(form.value.serviceIntervalDays) || 365,
       serviceIntervalKm: Number(form.value.serviceIntervalKm) || 15000,
+      technicalCheckIntervalDays: Number(form.value.technicalCheckIntervalDays) || 365,
       currentKm: form.value.currentKm ? Number(form.value.currentKm) : 0,
     };
     const saved = isEdit
@@ -162,6 +164,14 @@ async function submit() {
           <input v-model="form.serviceIntervalKm" type="number" class="dh-input data" />
         </div>
       </div>
+      <div>
+        <label class="dh-label">Technical check interval (days)</label>
+        <input v-model="form.technicalCheckIntervalDays" type="number" class="dh-input data" />
+        <p class="mt-1 text-xs text-muted">
+          Prefills each check's next-due date. Any check can override it with the date printed on
+          its certificate.
+        </p>
+      </div>
       <div class="mt-4 flex justify-end gap-2">
         <button type="button" class="dh-btn dh-btn-ghost" @click="emit('close')">Cancel</button>
         <button type="submit" :disabled="saving" class="dh-btn dh-btn-primary">