feat: add InkPanel Mini 1.54-inch 200x200 support

[CtrlAltcouk]

Goal

Add the Seeed XIAO ESP32-S3 + ePaper Driver Board + 1.54-inch 200x200 SSD1681 as a second InkPanel display option.

Hard compatibility requirement

Existing wft0583-800x480-mono panels retain their current four-widget renderer, 48,000-byte wire framebuffer, old-V2 display driver, device behaviour and published production firmware package. Mini is additive and uses a dedicated 200x200 renderer/firmware path.

Implemented

• register ssd1681-200x200-mono (200x200 / 5,000 bytes / one widget)
• advance device persistence V2 -> V3 without modifying frozen V1/V2 schemas
• preserve all existing four-widget configs during migration
• add backwards-compatible X-InkPanel-Profile enrolment negotiation
• add separate 200x200 single-widget rendering and Mini enrolment frame
• make FrameService/manage routes profile-aware while preserving the large profile contract
• add Studio single-widget mode with square live preview
• reuse remembered widget settings and existing write-only provider credentials
• add shared dual-target firmware architecture and dedicated SSD1681 MiniEPD
• keep existing OldV2EPD and the existing 800x480 template untouched
• add standard XIAO ESP32-S3 Mini target with separate 8 MB partition map
• omit unavailable Mini battery telemetry instead of fabricating a reading
• publish both firmware targets atomically: full-size at firmware/dist, Mini at firmware/dist/mini
• add target-isolated firmware APIs and explicit WebFlash hardware selection
• preserve the historical full-size firmware manifest/binary endpoints
• add Mini firmware, manifest, WebFlash and 5,000-byte/ETag/304 regression tests
• update README/flashing/Mini documentation for both hardware profiles

Release gates

• Server/typecheck/Node/browser test suite
• Timezone matrix
• Existing 7.5-inch firmware compiles and remains version 0.1.4
• Mini firmware compiles for esp32:esp32:XIAO_ESP32S3
• Production build publishes and verifies both full-size and Mini packages
• Real 1.54-inch panel performs the production MiniEPD full refresh with correct pattern/polarity/orientation
• Real panel reaches PASS: driver refresh and sleep commands completed.
• Automated Mini contract verifies exactly 5,000 bytes + ETag + subsequent HTTP 304/no body
• Explicit WebFlash hardware selection and separate Mini provisioning address (0x7FF000)
• Existing full-size provisioning remains 0xFFF000
• Final full regression CI passed on this exact head (CI #226)
• Post-merge live validation: deploy via Settings -> Update now, WebFlash the Mini, verify one-widget Studio + real frame + no visible refresh on unchanged content

The remaining live validation requires the Mini-aware server and WebFlash package on main, so it is intentionally the post-merge acceptance test.