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/document_processors/tesseract.py

@@ -71,7 +71,7 @@ class TesseractProcessor(DocumentProcessor):
             )
 
         self.default_lang = default_lang
-        logger.info(f"Initialized TesseractProcessor: lang={default_lang}")
+        logger.info("Initialized TesseractProcessor: lang=%s", default_lang)
 
     @property
     def name(self) -> str:
@@ -137,8 +137,9 @@ class TesseractProcessor(DocumentProcessor):
             }
 
             logger.debug(
-                f"Tesseract OCR completed: {len(text)} chars, "
-                f"confidence={avg_confidence:.1f}%"
+                "Tesseract OCR completed: %s chars, confidence=%s%%",
+                len(text),
+                format(avg_confidence, ".1f"),
             )
 
             return ProcessingResult(
@@ -149,7 +150,7 @@ class TesseractProcessor(DocumentProcessor):
             )
 
         except Exception as e:
-            logger.error(f"Tesseract processing failed: {e}")
+            logger.error("Tesseract processing failed: %s", e)
             raise ProcessorError(f"OCR failed: {str(e)}") from e
 
     async def health_check(self) -> bool: