docs(reset): "hold until the screen starts to flash" terminology

Renames the user-facing description of the BOOT-button factory reset
across the codebase. The threshold remains 5 s (RESET_HOLD_MS) but
"hold for 5 seconds" misled users: total wall-clock time-to-visible-
change includes ~20 s of e-ink redraw after the threshold fires, and
a too-short press now wakes the device into a normal poll cycle (a
side effect of the EXT0 wakeup we just added). "Until the screen
starts to flash" matches what the user actually sees.

  - Remove-this-frame modal gains a small aside describing the
    physical reset for the new owner, with the new terminology and
    a callout that a brief tap just refreshes the image.
  - CLAUDE.md and the operation.h comment near the EXT0 wake call
    use the same phrasing.
  - feedback_reset_terminology.md memory locks the rule for future
    edits — never write "hold for 5 seconds" in user copy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -34,7 +34,7 @@ Build gifted e-ink frames that stay personal and current over time, with no ongo
 - Atomic image write: display only refreshes after complete confirmed transfer; last good image persists through outages
 - Deep sleep between pull cycles (see ESP32 deep sleep memory)
 - Status via border color: yellow = sync fail, red = no WiFi
-- 5-second button hold triggers re-provisioning (config wipe + AP mode)
+- Holding the BOOT button until the screen starts to flash triggers re-provisioning (config wipe + AP mode). Threshold is 5 s in firmware (RESET_HOLD_MS), but user-facing terminology is "hold until the screen flashes" because total wall-clock time-to-visible-change includes a ~20 s e-ink redraw, and a too-short press just wakes the device into a normal poll cycle.
 - Two-phase provisioning: AP mode (WiFi credentials) → STA mode (QR to account setup page)
 - Async image processing: Symfony Messenger (Doctrine transport), `max_retries: 1`
 - Image storage: `storage/images/{id}/{model}_{orientation}.bin`, relative paths in DB