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/observability/tracing.py

@@ -73,11 +73,12 @@ def setup_tracing(
             span_processor = BatchSpanProcessor(otlp_exporter)
             provider.add_span_processor(span_processor)
             logger.info(
-                f"OpenTelemetry tracing enabled with OTLP endpoint: {otlp_endpoint}"
+                "OpenTelemetry tracing enabled with OTLP endpoint: %s", otlp_endpoint
             )
         except Exception as e:
             logger.warning(
-                f"Failed to initialize OTLP exporter: {e}. Continuing without trace export."
+                "Failed to initialize OTLP exporter: %s. Continuing without trace export.",
+                e,
             )
     else:
         logger.info(
@@ -93,7 +94,7 @@ def setup_tracing(
     # Get and store tracer
     _tracer = trace.get_tracer(__name__)
 
-    logger.info(f"OpenTelemetry tracing initialized for service: {service_name}")
+    logger.info("OpenTelemetry tracing initialized for service: %s", service_name)
     return _tracer