Align Alembic metadata with models

[AlexKitipov]

Motivation

• Ensure Alembic autogeneration sees the full SQLAlchemy metadata and that model definitions match migrations so future alembic revision --autogenerate yields no unexpected drift.
• Consolidate all models on a single shared Base to avoid inconsistent metadata and type/index mismatches.

Description

• Import every model class in migrations/env.py so target_metadata = Base.metadata is fully populated during autogenerate and keep compare_type=True enabled.
• Point all model modules to the single declarative base by importing Base from app.database.base instead of app.database.
• Update the initial migration migrations/versions/0001_initial_schema.py to match the models (change links.click_count to BigInteger, make indexes/unique constraints match the model-generated names and uniqueness, and add/remove indexes so names and properties align).
• Chose to edit the initial migration (rather than add a corrective migration) because this repo only contains the initial schema migration, and aligning it removes drift for a clean autogenerate.

Testing

• Ran an SQLite upgrade + autogenerate drift check with DATABASE_URL=sqlite:///$tmp/test.db alembic upgrade head && DATABASE_URL=sqlite:///$tmp/test.db alembic check, and alembic check reported "No new upgrade operations detected" indicating no drift.
• Generated an autogenerate revision after the changes and confirmed the produced revision was empty (pass) for both attempts, indicating metadata/migration alignment.
• Compiled code with python -m compileall app migrations and ran the test suite with pytest, where all tests passed (8 passed).

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[chatgpt-codex-connector]

Add a forward migration for the BigInteger change

In any database that has already run revision 0001_initial_schema, Alembic will see the revision as applied and will not re-run this edited initial migration. Those environments therefore keep the old links.click_count INTEGER column while the model now expects BigInteger, so high-traffic links can still overflow at the 32-bit integer limit and Alembic drift checks will continue reporting the type mismatch. Please add a new migration that alters existing schemas instead of relying only on the rewritten initial revision.

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