Replace single preference table with global_preferences and route_preferences

[Copilot]

Split the monolithic preference table into two specialized preference types: global user preferences and location-specific route preferences.

Schema Changes

Old:

preference: id, user_id, prompt

New:

global_preferences: id, user_id, prompt
route_preferences: id, user_id, prompt, from_latitude, from_longitude, to_latitude, to_longitude

Implementation

• Models: Created GlobalPreference and RoutePreference with proper SQLAlchemy relationships
• Services: Extracted preference logic into global_preference_service and route_preference_service
• Migration: Drops preference table, creates both new tables with indexes and foreign keys
• API: Updated /users/preferences endpoint to use global preferences; route search now queries global preferences for user context
• Validation: Route preference coordinates validated with proper lat/lon bounds

Migration Impact

Existing preference data will be lost when migration runs. Users should export preferences before upgrading if data preservation is required.

All tests updated to use GlobalPreference model (84 passing).

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Update the preference schema and models</issue_title>
<issue_description>- Two new schemas / models:

global_preferences:
- id
- user_id
- prompt

route_preferences:
- id
- user_id
- prompt
- from_latitude
- from_longitude
- to_latitude
- to_longitude

• Apply previously implemented user preference logic for global_preferences.</issue_description>

<agent_instructions>Fix test compatibility due to change in preference to global_preference scheme.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Update the preference schema and models #53

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