fix(dashboard): persist Zielnote and make it more compact

[veniplex]

Summary

• The "Zielnote" (target grade) input on the dashboard's semester overview was only kept in component state, so it reset to the default (2.0) every time the user navigated away and back. It's now persisted per program in localStorage.
• The widget took up a full row as a bordered box. Shrunk it to a compact, single-line, low-emphasis inline control (smaller text/input, no border/box) matching the request that it be more "dezent".

Test plan

• npx tsc --noEmit
• npx eslint on changed files
• Manually verify in the browser: set a target grade, navigate to another page and back, confirm it's retained; visually confirm the control is compact and unobtrusive

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Generated by Claude Code

[veniplex]

Pushed a follow-up commit: the Zielnote is now persisted server-side in degree_program.grade_goal (new column, migration 0028_bouncy_hawkeye.sql), scoped per user via the existing program-ownership checks, instead of localStorage — so it now syncs across devices. Saved via a debounced updateGradeGoal server action mirroring the existing updateGradeScale pattern.

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Generated by Claude Code