Add Cyrillic/UTF-8 text support to SH1106Display

[strasharo]

Switches SH1106Display from Adafruit_SH110X/GFX to U8g2 so it can actually render Cyrillic (and other non-Latin UTF-8) text instead of falling back to block characters. Picks up on #1930 and the still-open #1439, where the author got SSD1306 working but didn't have SH1106 hardware to test against - I do, so this covers that gap.

What changed:

• font rendering now goes through U8g2 instead of Adafruit_GFX. Using the X11 "fixed" fonts (public domain, ISO10646/Unicode-encoded, full Basic Latin + Cyrillic coverage) at two sizes to roughly match the old font's small/large text sizes
• print()/getTextWidth() now use U8g2's UTF-8-aware drawUTF8()/getUTF8Width() instead of the old byte-per-char path
• overrode translateUTF8ToBlocks() to just pass the string through unchanged, since the display can render it properly now and doesn't need the block-character fallback
• fixed drawXbm() along the way - the icon/logo bitmaps in this codebase are packed MSB-first (Adafruit_GFX::drawBitmap() convention), but U8g2's own drawXBM() expects LSB-first, so icons came out completely garbled until I switched to U8g2's u8glib-compatible drawBitmap() instead, which uses the same MSB-first order

SH1106Display is shared by 7 boards (nano_g2_ultra, thinknode_m2, station_g2, wio-tracker-l1, lilygo_tbeam_1w, station_g3_esp32, lilygo_tbeam_supreme_SX1262), swapped the SH110X/GFX lib_deps for U8g2 on all of them. Built all 7 clean. Actually flash-tested on Wio Tracker L1 Pro and T-Beam Supreme since that's what I have on hand - confirmed Cyrillic text renders correctly (including a real message received over a channel), icons render correctly, and existing Latin-script screens still look right.

Not in scope here: long messages still don't wrap or scroll on this display, that's a separate thing I'll follow up with once this lands.

[strasharo]

Closing this for now - found a cleaner way to do this (wrapping the existing Adafruit_GFX driver with U8g2_for_Adafruit_GFX instead of swapping the whole rendering backend), going to rework it that way instead. Will open a new PR once it's ready.