Meshpocket morse port

[pelgraine]

Ports Morse-code input to the Heltec Meshpocket so the device can compose and send messages standalone (without a paired BLE companion), plus a handful of bug fixes and tuning improvements picked up along the way.

What's included

Meshpocket Morse input (main feature)

• New Morse compose mode for single-button devices — press duration distinguishes dot vs dash, inter-press silence distinguishes letter gap vs word gap.
• Visual feedback on the e-ink display showing the accumulated dot/dash buffer and decoded letters.
• Hold actions for BKSP / SEND / EXIT using escalating press durations (3s / 7s / 9s) to avoid accidental sends.
• Accompanying Morse user guide.

Meshpocket-specific fixes

• Added hardcoded preamble length override for narrow-bandwidth preset usage (32 symbols at SF ≤ 8, 16 otherwise) — matches the approach discussed in Lora longer preamble #1954.
• Re-added the Meshpocket repeater env to the build matrix.
• Powersaving fixes ported from Added Power Saving for NRF52 companions to have extra 30% battery life #2286.
• Updated firmware build date.

Morse timing / display tuning

• Word gap widened 2000ms → 3500ms to avoid natural inter-letter pauses triggering accidental spaces.
• Removed the "ready" → "keying…" display transition during active Morse input to eliminate unnecessary e-ink refresh blocks during dot/dash sequences.
• Alternative prosign-based action triggers: in addition to the escalating long-press durations (BKSP / SEND / EXIT), users can trigger the same actions by keying prosigns — HH for backspace, WW for send — which gives a more deliberate input path and avoids accidentally triggering an action when the user simply pauses mid-message.