fix: Better convey privacy in the Food Settings screen

[tshrrx]

What

Refactored UI to better convey privacy in Food Preferences page aligning with current release UI.

###Changes

• Simplified the On-device message. Made the message shorter and easier to understand.
• Added Privacy Icon for Emphasis. 'packages\smooth_app\assets\icons\privacy.png'
• Displayed the message using 'UserPreferencesItemSimple' in packages\smooth_app\lib\pages\preferences\user_preferences_food.dart.
• Applied custom styling using Container with theme-based colors.

Ready to roll out PR for new UI after merging of fix for New UI for the food preferences #6459

Screenshot

Before:

After:
-Dark Theme

-Light Theme

-Onboarding

Fixes bug(s)

• Fixes: Better convey privacy in the Food Settings screen (separate the ondevice msg, and add a lock or something to it) #5645

Part of

• Ensuring we are/remain best in class in privacy, GDPR… #4511
• Food preferences (Tracker issue) #506

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes missing coverage. Please review.

Project coverage is 5.89%. Comparing base (4d9c7fc) to head (9510ef9).
Report is 834 commits behind head on develop.

Files with missing lines	Patch %	Lines
...p/lib/pages/preferences/user_preferences_food.dart	0.00%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #6527      +/-   ##
==========================================
- Coverage     9.54%   5.89%   -3.66%     
==========================================
  Files          325     496     +171     
  Lines        16411   29586   +13175     
==========================================
+ Hits          1567    1743     +176     
- Misses       14844   27843   +12999     

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