feat(backend+frontend): add is_regex support to dictionary entries

Add support for regex-based dictionary entries across the full stack:

Backend:
- DictionaryEntry model: add is_regex column (Boolean, default False)
- DictionaryEntryCRUD: validate regex on add_entry(), compile on creation
- _enforce_dictionary: match by regex pattern when is_regex=True
- dictionary_filter: support is_regex in filter/query
- metrics: include is_regex entries in metrics calculations
- Alembic migration: 20260604_add_is_regex_to_dictionary_entries
- Merge migration: 351afb8f961a (merge is_regex + composite index heads)

Frontend:
- DictionaryDetailModel: add is_regex field to DictionaryEntry interface,
  EditForm, and addForm; sync edit/add form state with backend schema

backend/alembic/versions/20260604_add_is_regex_to_dictionary_entries.py

@@ -0,0 +1,38 @@
+"""Add is_regex column to dictionary_entries
+
+Revision ID: b2c3d4e5f6a7
+Revises: a1b2c3d4e5f6
+Create Date: 2026-06-04
+
+Add regex pattern support to terminology dictionary entries.
+When is_regex=True, source_term is treated as a regex pattern
+instead of a literal substring for matching and enforcement.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "b2c3d4e5f6a7"
+down_revision: Union[str, None] = "a1b2c3d4e5f6"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "dictionary_entries",
+        sa.Column(
+            "is_regex",
+            sa.Boolean(),
+            nullable=False,
+            server_default=sa.text("false"),
+            comment="Whether source_term is a regex pattern",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("dictionary_entries", "is_regex")

backend/alembic/versions/351afb8f961a_merge_is_regex_and_composite_index_heads.py

@@ -0,0 +1,28 @@
+"""merge is_regex and composite index heads
+
+Revision ID: 351afb8f961a
+Revises: b2c3d4e5f6a7, c7d8e9f0a1b2
+Create Date: 2026-06-04 14:50:00.004262
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '351afb8f961a'
+down_revision: Union[str, Sequence[str], None] = ('b2c3d4e5f6a7', 'c7d8e9f0a1b2')
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    pass
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    pass