huddle 1.2.5 — bigger attachments (50 MiB) + attach-by-path polish

• Larger attachments — the per-file cap goes from 1 MiB to 50 MiB. Chunks are now 128 KiB, keeping a full-size file at ~400 chunks — under the relay's per-recipient mailbox cap, so a big file still reaches an offline recipient. The whole file is held in memory on both ends and the receiver enforces its own cap, so a >1 MiB file only lands if both peers are on 1.2.5+. No relay change required (verified end-to-end against the live relay, including 3-member group fan-out + a multi-MiB round-trip).
• attach-by-path polish (from the 1.2.4 review). TUI + GUI share one ~-expansion helper (only ~ / ~/… expand); "attach by path" is guarded on being in a room; the GUI modal submits on Enter; empty input gives feedback; the in-app help no longer advertises a bare p that only works inside the picker.

All four crates bumped 1.2.4 → 1.2.5.