feat: add query parameter filtering to all collection endpoints

[AdityaAsopa]

Summary

Adds URL query parameter filtering to all five collection endpoints, making the API significantly more useful for consumers who need subsets of the data.

New filtering capability

Endpoint	Supported filters
/api/spacecrafts	status, orbit_type, mission_type, launch_vehicle
/api/launchers	vehicle_family
/api/customer_satellites	country, launcher
/api/centres	state
/api/spacecraft_missions	status, orbit_type, mission_type, launch_vehicle, launch_site

Example queries

/api/spacecrafts?status=active
/api/spacecrafts?orbit_type=GEO&status=decommissioned
/api/spacecraft_missions?mission_type=Remote+Sensing&orbit_type=SSO
/api/customer_satellites?country=Germany
/api/launchers?vehicle_family=PSLV
/api/centres?state=Karnataka

Behaviour

• Case-insensitive — ?status=Active and ?status=active are equivalent
• Composable — multiple filters narrow results (AND logic)
• Unknown params ignored — forward-compatible; adding new fields won't break old clients
• Empty array, not 404 — when filters match no records, returns { "spacecrafts": [] }

Backward compatibility

Calling any endpoint without query params returns the full collection exactly as before — no breaking changes.

Notes

This PR depends on the normalized data from PR #65. The filter values (GEO, SSO, active, PSLV, etc.) are only consistent and useful because the underlying data has been normalized to use consistent field names and values.

Test plan

• /api/spacecrafts?status=active returns only active spacecrafts
• /api/spacecrafts?orbit_type=GEO&status=active returns intersection
• /api/spacecrafts?status=ACTIVE (uppercase) returns same result
• /api/spacecrafts?unknown_param=foo returns full collection
• /api/spacecrafts?status=nonexistent returns { "spacecrafts": [] }
• All endpoints without params return same response as before