Add assigned-to-me bounty filter

[cybercraftsolutionsllc]

Summary

• adds myAssigned=true support to /gobounties/all
• requires an authenticated pubkey only when the assigned-to-me filter is requested, preserving the public bounty list behavior otherwise
• filters returned bounties to the authenticated user assignee and covers the handler auth gate with unit tests
• refreshes the generated database mock so the handler package compiles against the current database interface

Fixes #2436.

Validation

• go test ./handlers -run TestGetAllBountiesMyAssignedAuth -count=1
• go test ./handlers -run '^$' -count=1
• go test ./db -run '^$' -count=1
• git diff --check

[cybercraftsolutionsllc]

Closing this PR as a duplicate of the earlier submission #2773: #2773

I missed the existing PR during target triage. Sorry for the duplicate review load. The prior PR covers the same backend myAssigned filter support for /gobounties/all, so this one should not compete for the bounty or maintainer attention.