feat: initialiser le projet CVP (Next.js 14 + FastAPI + PostgreSQL)

- Frontend : Next.js 14 App Router, TypeScript strict, Tailwind 3, shadcn/ui, next-intl (fr/en)
- Backend : FastAPI, SQLAlchemy 2 async, Alembic, Pydantic 2, Python 3.11
- Infrastructure : Docker Compose (PostgreSQL 16 + Ollama)
- Tooling : ESLint + Prettier (frontend), Ruff (backend), pytest
- Structure complète des dossiers avec pages et routers placeholder

backend/app/db/migrations/README

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+Generic single-database configuration.

backend/app/db/migrations/env.py

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+from logging.config import fileConfig
+
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+
+from app.config import settings
+
+# This is the Alembic Config object
+config = context.config
+
+# Set the SQLAlchemy URL from our app config
+# Use the sync version (postgresql:// instead of postgresql+asyncpg://)
+config.set_main_option(
+    "sqlalchemy.url",
+    settings.database_url.replace("+asyncpg", ""),
+)
+
+# Interpret the config file for Python logging
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# Import all models here so Alembic can detect them
+# from app.models import Base  # uncomment when models are defined
+target_metadata = None  # replace with Base.metadata when models are defined
+
+
+def run_migrations_offline() -> None:
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    with connectable.connect() as connection:
+        context.configure(connection=connection, target_metadata=target_metadata)
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

backend/app/db/migrations/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}