Migrate to dmenu-flexipatch

Enables preprocessor-based patch management with the following patches:
- alpha: Transparency support
- border: Window border
- caseinsensitive: Case-insensitive matching by default
- center: Centered dmenu window
- ctrl_v_to_paste: Ctrl+V paste support
- fuzzymatch: Fuzzy matching
- highlight: Highlight matched text
- line_height: Configurable line height
- mouse_support: Mouse interaction
- numbers: Show item count
- password: Password input mode
- rejectnomatch: Reject non-matching input
- xresources: Runtime color configuration

Custom settings:
- Font: JetBrainsMono Nerd Font:size=14
- Colors: #2a4055 fg, #9CC2EC bg, #DEC292 selection
- Center enabled by default
- Border width: 2px