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/oauth_tools.py

@@ -266,7 +266,7 @@ async def _provision_nextcloud_access(ctx: Context, user_id: str) -> Provisionin
         )
 
     except Exception as e:
-        logger.error(f"Failed to initiate provisioning: {e}")
+        logger.error("Failed to initiate provisioning: %s", e)
         return ProvisioningResult(
             success=False,
             message=f"Failed to initiate provisioning: {str(e)}",
@@ -337,7 +337,7 @@ async def _revoke_nextcloud_access(ctx: Context, user_id: str) -> RevocationResu
             )
 
     except Exception as e:
-        logger.error(f"Failed to revoke access: {e}")
+        logger.error("Failed to revoke access: %s", e)
         return RevocationResult(
             success=False,
             message=f"Failed to revoke access: {str(e)}",
@@ -542,7 +542,7 @@ async def _check_logged_in(ctx: Context, user_id: str) -> str:
             return "Login cancelled by user."
 
     except Exception as e:
-        logger.error(f"Failed to check login status: {e}")
+        logger.error("Failed to check login status: %s", e)
         return f"Error checking login status: {str(e)}"