feat: integrate Modal Closer as injected browser script (#27)

Port the modalcloser abx-plugin as a SingleFile --browser-script rather
than a spawned Puppeteer daemon. No external extension download required.

Core behavior (singlefile.rs):
- MODAL_CLOSER_DIALOG_OVERRIDES: main-world <script> bridge (best-effort;
  blocked by strict script-src CSP) that overrides window.alert/confirm/
  prompt/print, nulls window.onbeforeunload, traps its setter, and wraps
  window.addEventListener to no-op 'beforeunload' registrations.
- MODAL_CLOSER_POLLING_SETUP: defines _archivr_mc_run() which runs two
  passes on every tick (immediate first run, then setInterval every 500 ms
  matching MODALCLOSER_POLL_INTERVAL default):
    Pass 1 (best-effort, CSP-sensitive): main-world <script> bridge calls
    Bootstrap/jQuery/jQuery UI/SweetAlert teardown APIs.
    Pass 2 (always, CSP-immune): isolated-world DOM mutations — Escape-key
    dispatch (Radix/Headless UI/Angular Material), backdrop clicks, full
    CSS selector hiding for 40+ named consent/overlay vendors, body
    scroll-lock reset. Direct DOM mutations need no inline script execution.
- resolve_modal_closer_config(): reads ARCHIVR_MODAL_CLOSER env var
  (default true); no external resource required.
- modal_closer_enabled: Option<bool> in CaptureConfig so Default::default()
  yields None (follow env var) rather than false.

Schema (database.rs):
- modal_closer_enabled column in auth DB instance_settings (default 1).
- Idempotent ALTER TABLE migration for existing databases.
- get/update_instance_settings updated (SELECT col 6, UPDATE param ?7).

HTTP (routes.rs):
- modal_closer_enabled in CaptureBody and UpdateInstanceSettingsBody.
- Per-capture body overrides global setting which overrides env var.

Frontend:
- SettingsView ExtensionsTab: third ext-card for Modal & Dialog Closer.
- CaptureDialog: per-capture toggle in Advanced Options, state initialized
  from server default, included in submitCapture payload.
- api.js: submitCapture forwards modal_closer_enabled to capture body.

Behavior vs original modalcloser daemon:
- Functionally identical on non-strict-CSP pages (the large majority).
- Gap: <script> bridge is subject to page CSP; page.evaluate() is not.
  On strict-CSP pages framework teardown and dialog overrides are no-ops;
  CSS selector hiding and Escape dispatch (Pass 2) always work.
- Gap: alert/confirm/prompt overridden to instant no-op vs CDP timed
  dialog.accept() with 1250 ms delay; irrelevant for archival in practice.

crates/archivr-core/src/database.rs

@@ -142,6 +142,8 @@ pub struct InstanceSettings {
     pub ublock_enabled: bool,
     /// Global default for cookie-consent banner dismissal via extension during WebPage captures.
     pub cookie_ext_enabled: bool,
+    /// Global default for modal-closer browser-script behavior during WebPage captures.
+    pub modal_closer_enabled: bool,
 }
 
 #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
@@ -468,7 +470,8 @@ pub fn initialize_auth_schema(conn: &Connection) -> Result<()> {
             public_archive_submission_enabled  INTEGER NOT NULL DEFAULT 0 CHECK (public_archive_submission_enabled IN (0, 1)),
             default_entry_visibility           INTEGER NOT NULL DEFAULT 2,
             ublock_enabled                     INTEGER NOT NULL DEFAULT 1 CHECK (ublock_enabled IN (0, 1)),
-            cookie_ext_enabled                 INTEGER NOT NULL DEFAULT 1 CHECK (cookie_ext_enabled IN (0, 1))
+            cookie_ext_enabled                 INTEGER NOT NULL DEFAULT 1 CHECK (cookie_ext_enabled IN (0, 1)),
+            modal_closer_enabled               INTEGER NOT NULL DEFAULT 1 CHECK (modal_closer_enabled IN (0, 1))
         );
 
         INSERT OR IGNORE INTO instance_settings
@@ -518,6 +521,11 @@ pub fn initialize_auth_schema(conn: &Connection) -> Result<()> {
         "ALTER TABLE instance_settings ADD COLUMN cookie_ext_enabled INTEGER NOT NULL DEFAULT 1",
         [],
     );
+    // Add modal_closer_enabled column to instance_settings if not present (idempotent migration)
+    let _ = conn.execute(
+        "ALTER TABLE instance_settings ADD COLUMN modal_closer_enabled INTEGER NOT NULL DEFAULT 1",
+        [],
+    );
 
     Ok(())
 }
@@ -745,7 +753,8 @@ pub fn get_instance_settings(conn: &Connection) -> Result<InstanceSettings> {
         "SELECT public_index_enabled, public_entry_content_enabled,
                 public_archive_submission_enabled, default_entry_visibility,
                 COALESCE(ublock_enabled, 1),
-                COALESCE(cookie_ext_enabled, 1)
+                COALESCE(cookie_ext_enabled, 1),
+                COALESCE(modal_closer_enabled, 1)
          FROM instance_settings WHERE id = 1",
         [],
         |row| {
@@ -756,6 +765,7 @@ pub fn get_instance_settings(conn: &Connection) -> Result<InstanceSettings> {
                 default_entry_visibility: row.get::<_, i64>(3)? as u32,
                 ublock_enabled: row.get::<_, i64>(4)? != 0,
                 cookie_ext_enabled: row.get::<_, i64>(5)? != 0,
+                modal_closer_enabled: row.get::<_, i64>(6)? != 0,
             })
         },
     )
@@ -770,7 +780,8 @@ pub fn update_instance_settings(conn: &Connection, settings: &InstanceSettings)
              public_archive_submission_enabled = ?3,
              default_entry_visibility = ?4,
              ublock_enabled = ?5,
-             cookie_ext_enabled = ?6
+             cookie_ext_enabled = ?6,
+             modal_closer_enabled = ?7
          WHERE id = 1",
         params![
             settings.public_index_enabled as i64,
@@ -779,6 +790,7 @@ pub fn update_instance_settings(conn: &Connection, settings: &InstanceSettings)
             settings.default_entry_visibility as i64,
             settings.ublock_enabled as i64,
             settings.cookie_ext_enabled as i64,
+            settings.modal_closer_enabled as i64,
         ],
     )?;
     Ok(())