Support commitments across projects, subprojects, contexts and tags

[Fingolfin7]

Motivation

• Allow users to attach commitments not only to projects but also to subprojects, contexts or tags so progress/streak/banking can be tracked across aggregation types.
• Keep existing per-project flows intact while enabling cross-aggregation reporting and reconciliation.

Description

• Added an aggregation_type field and optional one-to-one target fields (project, subproject, context, tag) to the Commitment model and added model-level clean() validation to require exactly one target and ensure the target belongs to the same user. (core/models.py)
• Introduced get_commitment_sessions_queryset() and updated get_commitment_progress(), calculate_commitment_streak() and reconcile_commitment() to aggregate sessions according to the selected aggregation_type (project membership, subproject relation, project context, or project tags). (core/utils.py)
• Extended the CommitmentForm to present aggregation_type plus per-user ModelChoiceFields for project/subproject/context/tag, normalize the chosen target during clean(), and initialize project-scoped creates when project_pk is provided. (core/forms.py)
• Updated create/update/delete views and URLs to support a generic create flow and to preserve project-scoped redirects when appropriate, and updated templates/dashboard to display target_name with the aggregation type. (core/views.py, core/urls.py, core/templates/core/*.html)
• Added a migration 0034_commitment_aggregation_type_commitment_context_and_more.py to alter the commitment schema. (core/migrations/0034_*.py)

Testing

• Ran migration generation with python manage.py makemigrations core which produced the migration for the schema changes successfully. (succeeded)
• Ran the focused commitment test suite python manage.py test core.tests.CommitmentViewTests core.tests.UpdateProjectViewCommitmentTests core.tests.ProjectsListViewCommitmentTests core.tests.CommitmentStreakTests and validated the tests passed. (succeeded)
• Attempted a Playwright UI screenshot to validate templates, but the headless Chromium process crashed in this environment, so no screenshot artifact was produced (environment limitation, not functional regression). (failed artifact capture)

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Codex Task