feat: enforce single tool type with port configuration

- Replace interfaces array with single interface_type string (web/terminal)
- Add requires_port boolean to indicate port/tunnel needs
- Create Alembic migration for database schema change
- Update backend model, API validation, and seed data
- Update frontend types and tool workshop UI with dropdown
- Add conditional port field rendering based on interface type
- Update all frontend and backend tests

OpenSpec change: enforce-single-tool-type-with-port-config
Quality gates: frontend typecheck PASS, lint PASS, tests 37/37 PASS

openspec/specs/frontend-foundation/spec.md

@@ -111,6 +111,37 @@ The system SHALL provide a dashboard overview.
   - Recent activity
   - Quick action buttons
 
+### Requirement: Tool Interface Type Dropdown
+The tool workshop SHALL provide a dropdown for selecting a single interface type.
+
+#### Scenario: Interface type dropdown
+- GIVEN the tool workshop page
+- WHEN a user creates or edits a tool type
+- THEN the interface type field is a dropdown (not checkboxes)
+- AND the options are "web" and "terminal"
+- AND only one option can be selected
+
+### Requirement: Conditional Port Fields
+The tool workshop SHALL conditionally show or hide port-related fields based on the selected interface type.
+
+#### Scenario: Web tool shows port fields
+- GIVEN a tool type with interface type "web"
+- WHEN the user views the tool editor
+- THEN the Default Port field is visible and required
+- AND port-related config fields are shown
+
+#### Scenario: Terminal tool hides port fields
+- GIVEN a tool type with interface type "terminal"
+- WHEN the user views the tool editor
+- THEN the Default Port field is hidden
+- AND port-related config fields are hidden or disabled
+
+#### Scenario: Changing interface type updates visibility
+- GIVEN a user changes interface type from "web" to "terminal"
+- WHEN the change is applied
+- THEN port fields are immediately hidden
+- AND any port value is preserved but not validated
+
 ## Dependencies
 
 - React 18+