Add crossbar-on-7 option to distinguish 1 from 7

[laz-]

Summary

• Adds a Crossbar on 7 toggle in watch settings (off by default)
• When enabled, draws a tapered diagonal crossbar through the middle of the scaled '7' glyph, making it visually distinct from '1' in the BrutalTime font
• Bumps settings storage version to v8 with a clean migration path (defaults to false for existing users)

Before / After

1 (reference)	7 — before	7 — after
tall, narrow, serif corners	identical shape to 1	crossbar cuts diagonally through the stem

Implementation

The crossbar is painted directly into the scaled glyph buffer (s_scale_buf) after scale_glyph() runs. Six pixel blocks in glyph-relative coordinates produce a 3-2-1 tapered bar:

col:  2 3 4
row 5: ■ ■ ■
row 6:   ■ ■
row 7:     ■

Each block is expanded to s_scale_x × s_scale_y pixels (4×5 on Pebble Time, 6×7 on Emery) matching the existing scaling system. The feature is gated behind #ifndef PBL_PLATFORM_APLITE consistent with the rest of the big-font scaling code.

Settings migration

CURRENT_SETTINGS_VERSION incremented from 7 → 8. The v7 → v8 upgrade path sets sevenCrossbar = false and re-saves, so no existing user sees a behavior change on update.

[laz-]