feat: preferences dialog, SQL formatter, and enhanced table context menu

- PreferencesDialog (Tools → Preferences, Ctrl+,): font family/size,
  word wrap, default page size, query timeout, max history, auto-commit;
  font changes apply live to all open editors via apply_settings() cascade
- CodeEditor and TableViewer now read initial values from settings singleton
- SQL formatter (≡ Format button): uses sqlparse to reindent and uppercase
  keywords; gracefully prompts to install sqlparse if missing
- Table viewer context menu: "Filter by this value" (populates WHERE and
  reloads), "Copy row as SQL INSERT" (ready-to-paste INSERT statements),
  renamed "Copy row" → "Copy row as TSV" for clarity

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/ui/table_viewer.py

@@ -21,6 +21,7 @@ from PyQt6.QtCore import (
 from PyQt6.QtGui import QColor, QBrush, QFont, QKeySequence, QShortcut
 
 from app.utils.worker import TableDataWorker
+from app.config.settings import get_settings
 
 
 # ─────────────────────────────────────────────────────────────────────────────
@@ -310,7 +311,8 @@ class TableViewer(QWidget):
         self._table    = table
         self._offset   = 0
         self._total    = 0
-        self._page_size = 100          # default
+        ps = get_settings().get("result_page_size", 100)
+        self._page_size = ps if ps > 0 else 10_000_000   # 0 → All
         self._model    = EditableTableModel()
         self._worker: TableDataWorker | None = None
         self._build_ui()
@@ -609,14 +611,22 @@ class TableViewer(QWidget):
 
     def _context_menu(self, pos):
         rows = self._selected_logical_rows()
+        idx  = self._table_view.indexAt(pos)
         menu = QMenu(self)
         menu.addAction("➕ Add Row",    self._add_row)
         if rows:
             menu.addAction("✏️ Edit Row",   self._edit_selected)
             menu.addAction("🗑️ Delete Row", self._delete_selected)
         menu.addSeparator()
+        if idx.isValid():
+            menu.addAction("🔍 Filter by this value",
+                           lambda: self._filter_by_cell(idx))
+        menu.addSeparator()
         menu.addAction("📋 Copy cell value", lambda: self._copy_cell(pos))
-        menu.addAction("📋 Copy row",        self._copy_selected_rows)
+        menu.addAction("📋 Copy row as TSV", self._copy_selected_rows)
+        if rows:
+            menu.addAction("📋 Copy row as SQL INSERT",
+                           self._copy_selected_as_insert)
         menu.exec(self._table_view.viewport().mapToGlobal(pos))
 
     # ── Double-click: edit ────────────────────────────────────────────────────
@@ -725,3 +735,39 @@ class TableViewer(QWidget):
             row_data = self._model.get_row_current(r)
             lines.append("\t".join("" if v is None else str(v) for v in row_data))
         QApplication.clipboard().setText("\n".join(lines))
+
+    def _copy_selected_as_insert(self):
+        rows = self._selected_logical_rows()
+        cols = self._model.column_names()
+        col_list = ", ".join(f'"{c}"' for c in cols)
+        statements = []
+        for r in rows:
+            row_data = self._model.get_row_current(r)
+            values = []
+            for v in row_data:
+                if v is None:
+                    values.append("NULL")
+                elif isinstance(v, (int, float)):
+                    values.append(str(v))
+                else:
+                    escaped = str(v).replace("'", "''")
+                    values.append(f"'{escaped}'")
+            statements.append(
+                f'INSERT INTO "{self._table}" ({col_list}) VALUES ({", ".join(values)});'
+            )
+        QApplication.clipboard().setText("\n".join(statements))
+
+    def _filter_by_cell(self, index):
+        if not index.isValid():
+            return
+        col_name = self._model.column_names()[index.column()]
+        val = self._model.data(index, Qt.ItemDataRole.DisplayRole)
+        if val is None:
+            clause = f'"{col_name}" IS NULL'
+        elif isinstance(val, str):
+            escaped = val.replace("'", "''")
+            clause = f'"{col_name}" = \'{escaped}\''
+        else:
+            clause = f'"{col_name}" = {val}'
+        self._filter_input.setText(clause)
+        self._apply_filter()