refactor: convert f-string logging to lazy %-style format (G004)

Sweep all 1676 G004 violations across 112 files, converting
`logger.<level>(f"…{x}…")` to `logger.<level>("…%s…", x)`.

Why: ruff rule G004 was added to pyproject.toml to enforce lazy
%-style logging — defers formatting until the log level is enabled
and lets structured log tooling match the unformatted template.

Conversion preserves rendered output byte-for-byte:
- `{x}` → `%s` + `x`
- `{x!r}` / `{x!s}` / `{x!a}` → `%r` / `%s` / `%a`
- Format specs (`{x:.2f}`, `{x:>10}`) → `%s` + `format(x, 'spec')`
  (printf-style specs aren't 1:1 with Python format specs, so we
  delegate to `format()` to keep identical output)
- Literal `%` → `%%`
- Concatenated f-strings (`f"a {x} " "b"`) flattened
- Trailing kwargs (`exc_info=True`) preserved

Verified:
- `uv run ruff check --select G004` → 0 violations
- `uv run ty check -- nextcloud_mcp_server` → passes
- `uv run pytest tests/unit/` → 1010 passed

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/server/auth_tools.py

@@ -116,7 +116,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
             )
             init_response = await flow_client.initiate()
         except Exception as e:
-            logger.error(f"Failed to initiate Login Flow v2: {e}")
+            logger.error("Failed to initiate Login Flow v2: %s", e)
             return ProvisionAccessResponse(
                 status="error",
                 message=f"Failed to start login flow: {e}",
@@ -227,7 +227,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
         try:
             session = await storage.get_login_flow_session(user_id)
         except Exception as e:
-            logger.error(f"Failed to check login flow session for {user_id}: {e}")
+            logger.error("Failed to check login flow session for %s: %s", user_id, e)
             return ProvisionStatusResponse(
                 status="error",
                 message=f"Failed to check login flow session: {e}",
@@ -264,7 +264,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
                 poll_token=session["poll_token"],
             )
         except Exception as e:
-            logger.error(f"Failed to poll Login Flow v2: {e}")
+            logger.error("Failed to poll Login Flow v2: %s", e)
             return ProvisionStatusResponse(
                 status="error",
                 message=f"Failed to check login status: {e}",
@@ -434,7 +434,7 @@ def register_auth_tools(mcp: FastMCP) -> None:
             )
             init_response = await flow_client.initiate()
         except Exception as e:
-            logger.error(f"Failed to initiate Login Flow v2 for scope update: {e}")
+            logger.error("Failed to initiate Login Flow v2 for scope update: %s", e)
             return UpdateScopesResponse(
                 status="error",
                 message=f"Failed to start re-provisioning flow: {e}",