v1.6.3

📡 Mesh SD persistence & clock hardening

• Contact mirror (/meshcore/contacts.bin, SD takes load priority over SPIFFS, deferred write from loop()) and joined hashtag channels (/meshcore/channels.txt, re-joined on boot).
• RTC sync guard against future-clock outliers (bootstrap + forward jumps < 1 h, backward only on a 3× advert consensus).
• Contact overflow fix: overwrite the oldest non-favorite when the table (64) is full instead of dropping new adverts.
• Console hashtag commands join / chan, plus a new i2cscan command. Verified on device: the T-Deck Pro V1.1 has no hardware RTC (0x51 empty).