feat(config): add forge config defaults and %l eol specifier

Problem: no configuration surface for forge link rendering, icons,
issue format, or self-hosted instances.

Solution: add `pending.ForgeConfig` class with per-forge `token`,
`icon`, `issue_format`, and `instances` fields. Add `%l` to the
default `eol_format` so forge labels render in virtual text.

lua/pending/config.lua

@@ -33,6 +33,17 @@
 ---@field profile? string
 ---@field region? string
 
+---@class pending.ForgeInstanceConfig
+---@field token? string
+---@field icon? string
+---@field issue_format? string
+---@field instances? string[]
+
+---@class pending.ForgeConfig
+---@field github? pending.ForgeInstanceConfig
+---@field gitlab? pending.ForgeInstanceConfig
+---@field codeberg? pending.ForgeInstanceConfig
+
 ---@class pending.SyncConfig
 ---@field remote_delete? boolean
 ---@field gcal? pending.GcalConfig
@@ -90,6 +101,7 @@
 ---@field view pending.ViewConfig
 ---@field max_priority? integer
 ---@field sync? pending.SyncConfig
+---@field forge? pending.ForgeConfig
 ---@field icons pending.Icons
 
 ---@class pending.config
@@ -106,7 +118,7 @@ local defaults = {
   max_priority = 3,
   view = {
     default = 'category',
-    eol_format = '%c  %r  %d',
+    eol_format = '%l  %c  %r  %d',
     category = {
       order = {},
       folding = true,
@@ -141,6 +153,23 @@ local defaults = {
     priority_down = '<C-x>',
   },
   sync = {},
+  forge = {
+    github = {
+      icon = '',
+      issue_format = '%i %o/%r#%n',
+      instances = {},
+    },
+    gitlab = {
+      icon = '',
+      issue_format = '%i %o/%r#%n',
+      instances = {},
+    },
+    codeberg = {
+      icon = '',
+      issue_format = '%i %o/%r#%n',
+      instances = {},
+    },
+  },
   icons = {
     pending = ' ',
     done = 'x',