feat: Add currency management feature with CRUD operations

- Introduced a new template for currency overview and management (`currencies.html`).
- Updated footer to include attribution to AllYouCanGET.
- Added "Currencies" link to the main navigation header.
- Implemented end-to-end tests for currency creation, update, and activation toggling.
- Created unit tests for currency API endpoints, including creation, updating, and activation toggling.
- Added a fixture to seed default currencies for testing.
- Enhanced database setup tests to ensure proper seeding and migration handling.

tests/e2e/test_currencies.py

@@ -0,0 +1,130 @@
+import random
+import string
+
+from playwright.sync_api import Page, expect
+
+
+def _unique_currency_code(existing: set[str]) -> str:
+    """Generate a unique three-letter code not present in *existing*."""
+    alphabet = string.ascii_uppercase
+    for _ in range(100):
+        candidate = "".join(random.choices(alphabet, k=3))
+        if candidate not in existing and candidate != "USD":
+            return candidate
+    raise AssertionError(
+        "Unable to generate a unique currency code for the test run.")
+
+
+def _metric_value(page: Page, element_id: str) -> int:
+    locator = page.locator(f"#{element_id}")
+    expect(locator).to_be_visible()
+    return int(locator.inner_text().strip())
+
+
+def _expect_feedback(page: Page, expected_text: str) -> None:
+    page.wait_for_function(
+        "expected => {"
+        "  const el = document.getElementById('currency-form-feedback');"
+        "  if (!el) return false;"
+        "  const text = (el.textContent || '').trim();"
+        "  return !el.classList.contains('hidden') && text === expected;"
+        "}",
+        arg=expected_text,
+    )
+    feedback = page.locator("#currency-form-feedback")
+    expect(feedback).to_have_text(expected_text)
+
+
+def test_currency_workflow_create_update_toggle(page: Page) -> None:
+    """Exercise create, update, and toggle flows on the currency settings page."""
+    page.goto("/ui/currencies")
+    expect(page).to_have_title("Currencies · CalMiner")
+    expect(page.locator("h2:has-text('Currency Overview')")).to_be_visible()
+
+    code_cells = page.locator("#currencies-table-body tr td:nth-child(1)")
+    existing_codes = {text.strip().upper()
+                      for text in code_cells.all_inner_texts()}
+
+    total_before = _metric_value(page, "currency-metric-total")
+    active_before = _metric_value(page, "currency-metric-active")
+    inactive_before = _metric_value(page, "currency-metric-inactive")
+
+    new_code = _unique_currency_code(existing_codes)
+    new_name = f"Test Currency {new_code}"
+    new_symbol = new_code[0]
+
+    page.fill("#currency-form-code", new_code)
+    page.fill("#currency-form-name", new_name)
+    page.fill("#currency-form-symbol", new_symbol)
+    page.select_option("#currency-form-status", "true")
+
+    with page.expect_response("**/api/currencies/") as create_info:
+        page.click("button[type='submit']")
+    create_response = create_info.value
+    assert create_response.status == 201
+
+    _expect_feedback(page, "Currency created successfully.")
+
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-total').textContent.trim()) === expected",
+        arg=total_before + 1,
+    )
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-active').textContent.trim()) === expected",
+        arg=active_before + 1,
+    )
+
+    row = page.locator("#currencies-table-body tr").filter(has_text=new_code)
+    expect(row).to_be_visible()
+    expect(row.locator("td").nth(3)).to_have_text("Active")
+
+    # Switch to update mode using the existing currency option.
+    page.select_option("#currency-form-existing", new_code)
+    updated_name = f"{new_name} Updated"
+    updated_symbol = f"{new_symbol}$"
+    page.fill("#currency-form-name", updated_name)
+    page.fill("#currency-form-symbol", updated_symbol)
+    page.select_option("#currency-form-status", "false")
+
+    with page.expect_response(f"**/api/currencies/{new_code}") as update_info:
+        page.click("button[type='submit']")
+    update_response = update_info.value
+    assert update_response.status == 200
+
+    _expect_feedback(page, "Currency updated successfully.")
+
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-active').textContent.trim()) === expected",
+        arg=active_before,
+    )
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-inactive').textContent.trim()) === expected",
+        arg=inactive_before + 1,
+    )
+
+    expect(row.locator("td").nth(1)).to_have_text(updated_name)
+    expect(row.locator("td").nth(2)).to_have_text(updated_symbol)
+    expect(row.locator("td").nth(3)).to_contain_text("Inactive")
+
+    toggle_button = row.locator("button[data-action='toggle']")
+    expect(toggle_button).to_have_text("Activate")
+
+    with page.expect_response(f"**/api/currencies/{new_code}/activation") as toggle_info:
+        toggle_button.click()
+    toggle_response = toggle_info.value
+    assert toggle_response.status == 200
+
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-active').textContent.trim()) === expected",
+        arg=active_before + 1,
+    )
+    page.wait_for_function(
+        "expected => Number(document.getElementById('currency-metric-inactive').textContent.trim()) === expected",
+        arg=inactive_before,
+    )
+
+    _expect_feedback(page, f"Currency {new_code} activated.")
+
+    expect(row.locator("td").nth(3)).to_contain_text("Active")
+    expect(row.locator("button[data-action='toggle']")
+           ).to_have_text("Deactivate")