Daytime (manual) alignment screen (#455)

[brickbots]

Closes #455.

Adds a no-solve alignment path for daylight setup. The user points the scope at a distant object centred in the eyepiece, finds where the rigidly-mounted camera sees it, and marks that pixel by eye — writing it straight to target_pixel, the same destination the solve-based UIAlign / align_on_radec reaches (shared_state.set_target_pixel() + config["target_pixel"], stored as (Y, X) in the 512px native frame).

What's here

UIAlignDaytime (ui/align_daytime.py), wired as "Align (Day)" right after "Align" in the Start menu (stateful, preload). Like the solve-based screen it starts inactive — SQUARE begins the process. Then:

• Coarse: up to 3 rounds of 2×2 quadrant picks using keypad corners (7 TL, 9 TR, 1 BL, 3 BR — TKL layout), each round shrinking the region to the legibility floor (~16px cells on the 128 panel, ~22px on 176).
• Fine: the first arrow press (or the 3rd round) switches to 1-display-pixel nudging.
• SQUARE saves and exits; 0 cancels. +/- override exposure; long-press marking menu offers Center and Exp Auto.

Supporting changes

• ui/camera_render.py — shared crop/zoom/resize helper factored out of UIPreview (Focus screen behaviour preserved, pixel-identical). Daytime renders the frame full-brightness grayscale (no red night-vision mask — dark adaptation is irrelevant in daylight).
• camera_interface.py / camera_pi.py — new set_exp:native drives picamera2's native auto-exposure for daylight, with a fixed short-exposure fallback on backends without it (debug/none). set_camera_config now clears AeEnable on Pi so manual exposure (exp_up/exp_dn/set_exp:<us>) always overrides native AE. Exposure is saved on entry and restored on exit (active/inactive).
• Docs — quick-start "Daytime alignment" section + 2 screenshots; CONTEXT.md glossary terms (Daytime vs Solve-based alignment; keypad layout) from the design session.
• i18n — new UI strings wrapped in _(); Babel extract/update/compile run.
• Tests — tests/test_align_daytime.py: quadrant subdivision, display→native (Y, X) conversion at 128/176, and the camera-render helper.

Verification

• New unit tests + the UI smoke harness (incl. the all-modules coverage guard) pass; ruff check clean; mypy clean on the new files (not mypy-ignored).
• Ran the headless app: confirmed grayscale rendering and all states (inactive → quadrant grid → shrunk region → fine crosshair), plus a deterministic isolation test proving the full key flow writes target_pixel = (Y, X) to shared_state + config and restores the prior exposure on exit.

Reviewer notes

• The bulk of the .po diff is location-comment refresh — the catalogs hadn't been re-extracted since 2026-05-24, so running the documented nox -s babel pipeline updated #: line references across the whole file. The only content additions are the daytime-align UI strings (left as Babel's #, fuzzy → English fallback for translators to review).
• There is pre-existing ruff format drift in menu_structure.py (IMU-settings comments, ~line 1090) left untouched to keep this diff focused; nox -s format auto-fixes it.

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