feat(billing): A1+A3 — payment_products table + provider-agnostic price lookups

- Migration 0028: create payment_products table, copy paddle_products rows
- Add STRIPE_SECRET_KEY, STRIPE_PUBLISHABLE_KEY, STRIPE_WEBHOOK_SECRET config
- Make PAYMENT_PROVIDER read from env (was hardcoded "paddle")
- Add get_price_id() / get_all_price_ids() querying payment_products
- Keep get_paddle_price() as deprecated fallback alias

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/padelnomics/core.py

@@ -49,13 +49,17 @@ class Config:
     MAGIC_LINK_EXPIRY_MINUTES: int = int(os.getenv("MAGIC_LINK_EXPIRY_MINUTES", "15"))
     SESSION_LIFETIME_DAYS: int = int(os.getenv("SESSION_LIFETIME_DAYS", "30"))
 
-    PAYMENT_PROVIDER: str = "paddle"
+    PAYMENT_PROVIDER: str = _env("PAYMENT_PROVIDER", "paddle")
 
     PADDLE_API_KEY: str = os.getenv("PADDLE_API_KEY", "")
     PADDLE_CLIENT_TOKEN: str = os.getenv("PADDLE_CLIENT_TOKEN", "")
     PADDLE_WEBHOOK_SECRET: str = os.getenv("PADDLE_WEBHOOK_SECRET", "")
     PADDLE_ENVIRONMENT: str = _env("PADDLE_ENVIRONMENT", "sandbox")
 
+    STRIPE_SECRET_KEY: str = os.getenv("STRIPE_SECRET_KEY", "")
+    STRIPE_PUBLISHABLE_KEY: str = os.getenv("STRIPE_PUBLISHABLE_KEY", "")
+    STRIPE_WEBHOOK_SECRET: str = os.getenv("STRIPE_WEBHOOK_SECRET", "")
+
     UMAMI_API_URL: str = os.getenv("UMAMI_API_URL", "https://umami.padelnomics.io")
     UMAMI_API_TOKEN: str = os.getenv("UMAMI_API_TOKEN", "")
     UMAMI_WEBSITE_ID: str = "4474414b-58d6-4c6e-89a1-df5ea1f49d70"
@@ -722,16 +726,39 @@ async def purge_deleted(table: str, days: int = 30) -> int:
 # =============================================================================
 
 
+async def get_price_id(key: str, provider: str = None) -> str | None:
+    """Look up a provider price ID by product key from the payment_products table."""
+    provider = provider or config.PAYMENT_PROVIDER
+    row = await fetch_one(
+        "SELECT provider_price_id FROM payment_products WHERE provider = ? AND key = ?",
+        (provider, key),
+    )
+    return row["provider_price_id"] if row else None
+
+
+async def get_all_price_ids(provider: str = None) -> dict[str, str]:
+    """Load all price IDs for a provider as a {key: price_id} dict."""
+    provider = provider or config.PAYMENT_PROVIDER
+    rows = await fetch_all(
+        "SELECT key, provider_price_id FROM payment_products WHERE provider = ?",
+        (provider,),
+    )
+    return {r["key"]: r["provider_price_id"] for r in rows}
+
+
 async def get_paddle_price(key: str) -> str | None:
-    """Look up a Paddle price ID by product key from the paddle_products table."""
+    """Deprecated: use get_price_id(). Falls back to paddle_products for pre-migration DBs."""
+    result = await get_price_id(key, provider="paddle")
+    if result:
+        return result
+    # Fallback to old table if payment_products not yet populated
     row = await fetch_one("SELECT paddle_price_id FROM paddle_products WHERE key = ?", (key,))
     return row["paddle_price_id"] if row else None
 
 
 async def get_all_paddle_prices() -> dict[str, str]:
-    """Load all Paddle price IDs as a {key: price_id} dict."""
-    rows = await fetch_all("SELECT key, paddle_price_id FROM paddle_products")
-    return {r["key"]: r["paddle_price_id"] for r in rows}
+    """Deprecated: use get_all_price_ids()."""
+    return await get_all_price_ids(provider="paddle")
 
 
 # =============================================================================

web/src/padelnomics/migrations/versions/0028_generalize_payment_products.py

@@ -0,0 +1,33 @@
+"""Migration 0028: Generalize paddle_products → payment_products.
+
+New table supports multiple payment providers (paddle, stripe).
+Existing paddle_products rows are copied with provider='paddle'.
+The old paddle_products table is kept (no drop) for backwards compatibility.
+"""
+
+
+def up(conn) -> None:
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS payment_products (
+            id                  INTEGER PRIMARY KEY AUTOINCREMENT,
+            provider            TEXT NOT NULL,
+            key                 TEXT NOT NULL,
+            provider_product_id TEXT NOT NULL,
+            provider_price_id   TEXT NOT NULL,
+            name                TEXT NOT NULL,
+            price_cents         INTEGER NOT NULL,
+            currency            TEXT NOT NULL DEFAULT 'EUR',
+            billing_type        TEXT NOT NULL,
+            created_at          TEXT NOT NULL DEFAULT (datetime('now')),
+            UNIQUE(provider, key)
+        )
+    """)
+
+    # Copy existing paddle_products rows
+    conn.execute("""
+        INSERT OR IGNORE INTO payment_products
+            (provider, key, provider_product_id, provider_price_id, name, price_cents, currency, billing_type, created_at)
+        SELECT
+            'paddle', key, paddle_product_id, paddle_price_id, name, price_cents, currency, billing_type, created_at
+        FROM paddle_products
+    """)