feat(print-options): add "Auto" state to bed levelling, flow & nozzle-offset calibration

Bed levelling, flow calibration, and nozzle-offset calibration were on/off
only, so the sole way to run bed levelling was to force a full level before
every print. Bambu Studio has always offered a third "Auto" state that lets
the printer skip the calibration when it was done recently -- the state most
users actually want. Make these three options tri-state (off/on/auto),
defaulting to auto, and leave vibration/layer-inspect/timelapse as on/off
(Bambu Studio exposes no auto for those).

Wire encoding follows Bambu Studio's source exactly: each option sends a JSON
bool (true only for "on") plus a companion int -- off=0, on=1, auto=2. The
bool fields stay booleans (the #1478 H2S regression); only the companion int
widened from {0,1} to {0,1,2}. #1721's observation that stage 8/39 stays
queued when sending 2 is the auto contract (queued, skipped at runtime if
recent), not a broken "off".

- schemas: TriState = Literal[off/on/auto] with a BeforeValidator coercing
  legacy bool / 0-1 / true-false so old clients and un-migrated rows validate
- model + migration: boolean columns -> String; SQLite via column affinity +
  data backfill, PostgreSQL via ALTER COLUMN TYPE guarded on information_schema
  (verified on both dialects); settings rows normalised true/false -> on/off
- MQTT: start_print takes the tri-state strings and emits the paired bool+int
- Virtual Printer: reconstructs the slicer's auto/on/off from the int companion
  (auto_bed_leveling / extrude_cali_flag) in both capture paths
- frontend: CalibrationMode type; off/auto/on segmented controls in the print
  dialog, queue bulk-edit, and Settings -> Workflow; calibrationMode_* strings
  in all 11 locales

frontend/scripts/check-i18n-parity.mjs

@@ -142,6 +142,7 @@ function isAlwaysAllowedIdentical(value) {
 // UI labels are identical in DE. List below curates the legitimate ones.
 const DE_COGNATES = [
   '{{ams}} · Slot {{slot}}',  // #2587 runout slot label — "Slot" is the DE term too
+  'Auto',  // calibrationMode_auto — German UI uses the loanword (matches BambuStudio DE)
   'Name', 'Status', 'Tag', 'Tags', 'Online', 'Offline', 'Standard', 'Modus',
   'Stop', 'Reset', 'Test', 'Code', 'Token', 'Server', 'Port', 'Bug', 'Job',
   'Bambu Cloud', 'Orca Cloud',  // brand names — same in every locale