fix(frontend): make local view fit fill toggle effective

[xiaolefang-dm]

Summary

• apply Fit/Fill sizing to the local planning view container instead of always using a square
• preserve the local map aspect ratio from grid metadata
• keep manual target coordinate conversion aligned with the rendered content size

Screen.Recording.2026-05-19.at.21.21.13.mov

[github-actions]

cloc	github.com/AlDanial/cloc v 2.04 T=0.16 s (258.3 files/s, 38461.5 lines/s)

Language	files	blank	comment	code
Python	13	617	262	3457
Markdown	4	155	6	426
C++	4	60	38	409
Bourne Shell	15	41	9	272
Dockerfile	1	31	32	203
JSON	2	8	0	58
TOML	1	4	0	58
make	1	18	15	55
CMake	1	4	0	17
--------	--------	--------	--------	--------
SUM:	42	938	362	4955